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* High load and iowait but no disk access
@ 2005-08-29 13:42 Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:15 ` Re: High load and iowait but no disk access Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:25 ` Re: High load and iowait but no disk access Michael Stone <mstone+postgres@mathom.us>
2005-08-30 18:30 ` Re: High load and iowait but no disk access Woody Woodring <george.woodring@iglass.net>
2005-08-30 18:32 ` Re: High load and iowait but no disk access Josh Berkus <josh@agliodbs.com>
0 siblings, 4 replies; 12+ messages in thread
From: Rémy Beaumont @ 2005-08-29 13:42 UTC (permalink / raw)
To: pgsql-performance
We have been trying to pinpoint what originally seem to be a I/O
bottleneck but which now seems to be an issue with either Postgresql or
RHES 3.
We have the following test environment on which we can reproduce the
problem:
1) Test System A
Dell 6650 Quad Xeon Pentium 4
8 Gig of RAM
OS: RHES 3 update 2
Storage: NetApp FAS270 connected using an FC card using 10 disks
2) Test System B
Dell Dual Xeon Pentium III
2 Gig o RAM
OS: RHES 3 update 2
Storage: NetApp FAS920 connected using an FC card using 28 disks
Our Database size is around 30G.
The behavior we see is that when running queries that do random reads
on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000 kB/s
on sequential read operations on the netapps)
The stats of the NetApp do confirm that it is sitting idle. Doing an
strace on the Postgresql process shows that is it doing seeks and
reads.
So my question is where is this iowait time spent ?
Is there a way to pinpoint the problem in more details ?
We are able to reproduce this behavior with Postgresql 7.4.8 and 8.0.3
I have included the output of top,vmstat,strace and systat from the
Netapp from System B while running a single query that generates this
behavior.
Rémy
top output:
06:27:28 up 5 days, 16:59, 6 users, load average: 1.04, 1.30, 1.01
72 processes: 71 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 2.7% 0.0% 1.0% 0.1% 0.2% 46.0% 49.5%
cpu00 0.2% 0.0% 0.2% 0.0% 0.2% 2.2% 97.2%
cpu01 5.3% 0.0% 1.9% 0.3% 0.3% 89.8% 1.9%
Mem: 2061696k av, 2043936k used, 17760k free, 0k shrd,
3916k buff
1566332k actv, 296648k in_d, 30504k in_c
Swap: 16771584k av, 21552k used, 16750032k free
1933772k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU
COMMAND
30960 postgres 15 0 13424 10M 9908 D 2.7 0.5 2:00 1
postmaster
30538 root 15 0 1080 764 524 S 0.7 0.0 0:43 0 sshd
1 root 15 0 496 456 436 S 0.0 0.0 0:08 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0
migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1
migration/1
4 root 15 0 0 0 0 SW 0.0 0.0 0:01 0
keventd
5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0
ksoftirqd/0
6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1
ksoftirqd/1
9 root 15 0 0 0 0 SW 0.0 0.0 0:24 1
bdflush
7 root 15 0 0 0 0 SW 0.0 0.0 6:53 1 kswapd
8 root 15 0 0 0 0 SW 0.0 0.0 8:44 1 kscand
10 root 15 0 0 0 0 SW 0.0 0.0 0:13 0
kupdated
11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0
mdrecoveryd
17 root 15 0 0 0 0 SW 0.0 0.0 0:00 0
ahc_dv_0
vmstat output
procs memory swap io system
cpu
r b swpd free buff cache si so bi bo in cs us
sy id wa
0 1 21552 17796 4872 1931928 2 3 3 1 27 6 2
1 7 3
0 1 21552 18044 4880 1931652 0 0 1652 0 397 512 1
2 50 47
0 1 21552 17976 4896 1931664 0 0 2468 0 407 552 2
2 50 47
1 0 21552 17984 4896 1931608 0 0 2124 0 418 538 3
3 48 46
0 1 21552 18028 4900 1931536 0 0 1592 0 385 509 1
3 50 46
0 1 21552 18040 4916 1931488 0 0 1620 820 419 581 2
2 50 46
0 1 21552 17968 4916 1931536 0 4 1708 4 402 554 3
1 50 46
1 1 21552 18052 4916 1931388 0 0 1772 0 409 531 3
1 49 47
0 1 21552 17912 4924 1931492 0 0 1772 0 408 565 3
1 48 48
0 1 21552 17932 4932 1931440 0 4 1356 4 391 545 5
0 49 46
0 1 21552 18320 4944 1931016 0 4 1500 840 414 571 1
1 48 50
0 1 21552 17872 4944 1931440 0 0 2116 0 392 496 1
5 46 48
0 1 21552 18060 4944 1931232 0 0 2232 0 423 597 1
2 48 49
1 1 21552 17684 4944 1931584 0 0 1752 0 395 537 1
1 50 48
0 1 21552 18000 4944 1931240 0 0 1576 0 401 549 0
1 50 49
NetApp stats:
CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s
Cache Cache CP CP Disk DAFS FCP iSCSI FCP kB/s
in out read write read write
age hit time ty util in out
2% 0 0 0 139 0 0 2788 0 0 0
3 96% 0% - 15% 0 139 0 3 2277
2% 0 0 0 144 0 0 2504 0 0 0
3 96% 0% - 18% 0 144 0 3 2150
2% 0 0 0 130 0 0 2212 0 0 0
3 96% 0% - 13% 0 130 0 3 1879
3% 0 0 0 169 0 0 2937 80 0 0
3 96% 0% - 13% 0 169 0 4 2718
2% 0 0 0 139 0 0 2448 0 0 0
3 96% 0% - 12% 0 139 0 3 2096
2% 0 0 0 137 0 0 2116 0 0 0
3 96% 0% - 10% 0 137 0 3 1892
3% 0 0 0 107 0 0 2660 812 0 0
3 96% 24% T 20% 0 107 0 3 1739
2% 0 0 0 118 0 0 1788 0 0 0
3 96% 0% - 13% 0 118 0 3 1608
2% 0 0 0 136 0 0 2228 0 0 0
3 96% 0% - 11% 0 136 0 3 2018
2% 0 0 0 119 0 0 1940 0 0 0
3 96% 0% - 13% 0 119 0 3 1998
2% 0 0 0 136 0 0 2175 0 0 0
3 96% 0% - 14% 0 136 0 3 1929
2% 0 0 0 133 0 0 1924 0 0 0
3 96% 0% - 19% 0 133 0 3 2292
2% 0 0 0 115 0 0 2044 0 0 0
3 96% 0% - 11% 0 115 0 3 1682
2% 0 0 0 134 0 0 2256 0 0 0
3 96% 0% - 12% 0 134 0 3 2096
2% 0 0 0 112 0 0 2184 0 0 0
3 96% 0% - 12% 0 112 0 3 1633
2% 0 0 0 163 0 0 2348 0 0 0
3 96% 0% - 13% 0 163 0 4 2421
2% 0 0 0 120 0 0 2056 184 0 0
3 96% 8% T 14% 0 120 0 3 1703
strace output:
read(55, "\4\0\0\0\10fm}\1\0\0\0p\0\264\0\0 \2 \230\236\320\0020"...,
8192) = 8192
_llseek(55, 857997312, [857997312], SEEK_SET) = 0
read(55, "\4\0\0\0\\\315\321|\1\0\0\0p\0\354\0\0 \2 \250\236\260"...,
8192) = 8192
_llseek(55, 883220480, [883220480], SEEK_SET) = 0
read(55, "\4\0\0\0T\17a~\1\0\0\0p\0\20\1\0 \2 \270\236\220\2D\235"...,
8192) = 8192
_llseek(55, 858005504, [858005504], SEEK_SET) = 0
read(55, "\4\0\0\0\300\356\321|\1\0\0\0p\0\330\0\0 \2 \260\236\240"...,
8192) = 8192
_llseek(55, 857964544, [857964544], SEEK_SET) = 0
read(55, "\4\0\0\0lH\321|\1\0\0\0p\0<\1\0 \2 \300\236\200\2p\235"...,
8192) = 8192
_llseek(55, 857956352, [857956352], SEEK_SET) = 0
read(55, "\4\0\0\0l\'\321|\1\0\0\0p\0\320\0\0 \2 \260\236\240\2\\"...,
8192) = 8192
_llseek(55, 910802944, [910802944], SEEK_SET) = 0
read(55, "\4\0\0\0\10}\25\200\1\0\0\0l\0\274\1\0 \2 \250\236\260"...,
8192) = 8192
_llseek(55, 857948160, [857948160], SEEK_SET) = 0
read(55, "\4\0\0\0\370\5\321|\1\0\0\0p\0\350\0\0 \2 \230\236\320"...,
8192) = 8192
_llseek(56, 80371712, [80371712], SEEK_SET) = 0
read(56, "\4\0\0\0Lf \217\1\0\0\0p\0\f\1\0 \2 \250\236\260\2T\235"...,
8192) = 8192
read(102, "\2\0\34\0001\236\0\0\1\0\0\0\t\0\0\00020670\0\0\0B\6\0"...,
8192) = 8192
_llseek(55, 857939968, [857939968], SEEK_SET) = 0
read(55, "\4\0\0\0\244\344\320|\1\0\0\0l\0\230\1\0 \2 \244\236\270"...,
8192) = 8192
_llseek(55, 857923584, [857923584], SEEK_SET) = 0
read(55, "\4\0\0\0\224\242\320|\1\0\0\0p\0|\0\0 \2
\234\236\310\002"..., 8192) = 8192
_llseek(55, 57270272, [57270272], SEEK_SET) = 0
read(55, "\4\0\0\0\3204FK\1\0\0\0t\0\340\0\0 \2
\310\236j\2\214\235"..., 8192) = 8192
_llseek(55, 870727680, [870727680], SEEK_SET) = 0
read(55, "\4\0\0\0x>\233}\1\0\0\0p\0@\1\0 \2 \250\236\260\2X\235"...,
8192) = 8192
_llseek(55, 1014734848, [1014734848], SEEK_SET) = 0
read(55, "\4\0\0\0\34\354\201\206\1\0\0\0p\0p\0\0 \2 \264\236\230"...,
8192) = 8192
_llseek(55, 857874432, [857874432], SEEK_SET) = 0
read(55, "\4\0\0\0\214\331\317|\1\0\0\0l\0\324\1\0 \2 \224\236\330"...,
8192) = 8192
_llseek(55, 760872960, [760872960], SEEK_SET) = 0
read(55, "\4\0\0\0\30\257\321v\1\0\0\0p\0\230\0\0 \2 \234\236\310"...,
8192) = 8192
_llseek(55, 891715584, [891715584], SEEK_SET) = 0
read(55, "\4\0\0\0\370\220\347~\1\0\0\0p\0P\1\0 \2 \230\236\320\2"...,
8192) = 8192
_llseek(55, 857858048, [857858048], SEEK_SET) = 0
read(55, "\4\0\0\0\250\227\317|\1\0\0\0p\0\264\0\0 \2 \254\236\250"...,
8192) = 8192
_llseek(55, 666910720, [666910720], SEEK_SET) = 0
read(55, "\4\0\0\0x\206\3q\1\0\0\0p\0004\1\0 \2
\254\236\242\2P\235"..., 8192) = 8192
_llseek(55, 857841664, [857841664], SEEK_SET) = 0
read(55, "\4\0\0\0dT\317|\1\0\0\0p\0\224\0\0 \2 \214\236\350\2\30"...,
8192) = 8192
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
@ 2005-08-30 16:15 ` Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:19 ` Re: High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
3 siblings, 1 reply; 12+ messages in thread
From: Tom Lane @ 2005-08-30 16:15 UTC (permalink / raw)
To: Rémy Beaumont <remyb@medrium.com>; +Cc: pgsql-performance
=?ISO-8859-1?Q?R=E9my_Beaumont?= <remyb@medrium.com> writes:
> The stats of the NetApp do confirm that it is sitting idle.
Really?
> CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s
> Cache Cache CP CP Disk DAFS FCP iSCSI FCP kB/s
> in out read write read write
> age hit time ty util in out
> 2% 0 0 0 139 0 0 2788 0 0 0
> 3 96% 0% - 15% 0 139 0 3 2277
> 2% 0 0 0 144 0 0 2504 0 0 0
> 3 96% 0% - 18% 0 144 0 3 2150
> 2% 0 0 0 130 0 0 2212 0 0 0
> 3 96% 0% - 13% 0 130 0 3 1879
> 3% 0 0 0 169 0 0 2937 80 0 0
> 3 96% 0% - 13% 0 169 0 4 2718
> 2% 0 0 0 139 0 0 2448 0 0 0
> 3 96% 0% - 12% 0 139 0 3 2096
I know zip about NetApps, but doesn't the 8th column indicate pretty
steady disk reads?
regards, tom lane
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:15 ` Re: High load and iowait but no disk access Tom Lane <tgl@sss.pgh.pa.us>
@ 2005-08-30 16:19 ` Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:29 ` Re: High load and iowait but no disk access Tom Lane <tgl@sss.pgh.pa.us>
0 siblings, 1 reply; 12+ messages in thread
From: Rémy Beaumont @ 2005-08-30 16:19 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-performance
On 30-Aug-05, at 12:15, Tom Lane wrote:
> =?ISO-8859-1?Q?R=E9my_Beaumont?= <remyb@medrium.com> writes:
>> The stats of the NetApp do confirm that it is sitting idle.
>
> Really?
>
>> CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s
>> Cache Cache CP CP Disk DAFS FCP iSCSI FCP kB/s
>> in out read write read write
>> age hit time ty util in out
>> 2% 0 0 0 139 0 0 2788 0 0 0
>> 3 96% 0% - 15% 0 139 0 3 2277
>> 2% 0 0 0 144 0 0 2504 0 0 0
>> 3 96% 0% - 18% 0 144 0 3 2150
>> 2% 0 0 0 130 0 0 2212 0 0 0
>> 3 96% 0% - 13% 0 130 0 3 1879
>> 3% 0 0 0 169 0 0 2937 80 0 0
>> 3 96% 0% - 13% 0 169 0 4 2718
>> 2% 0 0 0 139 0 0 2448 0 0 0
>> 3 96% 0% - 12% 0 139 0 3 2096
>
> I know zip about NetApps, but doesn't the 8th column indicate pretty
> steady disk reads?
Yes, but they are very low.
At 15% usage, it's pretty much sitting idle if you consider that the OS
reports that one of the processor is spending more then 80% of it's
time in IOwait.
Rémy
>
> regards, tom lane
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:15 ` Re: High load and iowait but no disk access Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:19 ` Re: High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
@ 2005-08-30 16:29 ` Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:42 ` Re: High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
0 siblings, 1 reply; 12+ messages in thread
From: Tom Lane @ 2005-08-30 16:29 UTC (permalink / raw)
To: Rémy Beaumont <remyb@medrium.com>; +Cc: pgsql-performance
=?ISO-8859-1?Q?R=E9my_Beaumont?= <remyb@medrium.com> writes:
> On 30-Aug-05, at 12:15, Tom Lane wrote:
>> I know zip about NetApps, but doesn't the 8th column indicate pretty
>> steady disk reads?
> Yes, but they are very low.
Sure, but that's more or less what you'd expect if the thing is randomly
seeking all over the disk :-(. Just because it's a NetApp doesn't mean
it's got zero seek time.
You did not say what sort of query this is, but I gather that it's doing
an indexscan on a table that is not at all in index order. Possible
solutions involve reverting to a seqscan (have you forced the planner to
choose an indexscan here, either directly or by lowering random_page_cost?)
or CLUSTERing the table by the index (which would need to be repeated
periodically, so it's not a great answer).
regards, tom lane
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:15 ` Re: High load and iowait but no disk access Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:19 ` Re: High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:29 ` Re: High load and iowait but no disk access Tom Lane <tgl@sss.pgh.pa.us>
@ 2005-08-30 16:42 ` Rémy Beaumont <remyb@medrium.com>
0 siblings, 0 replies; 12+ messages in thread
From: Rémy Beaumont @ 2005-08-30 16:42 UTC (permalink / raw)
To: Tom Lane <tgl@sss.pgh.pa.us>; +Cc: pgsql-performance
On 30-Aug-05, at 12:29, Tom Lane wrote:
> =?ISO-8859-1?Q?R=E9my_Beaumont?= <remyb@medrium.com> writes:
>> On 30-Aug-05, at 12:15, Tom Lane wrote:
>>> I know zip about NetApps, but doesn't the 8th column indicate pretty
>>> steady disk reads?
>
>> Yes, but they are very low.
>
> Sure, but that's more or less what you'd expect if the thing is
> randomly
> seeking all over the disk :-(. Just because it's a NetApp doesn't mean
> it's got zero seek time.
Per NetApp, the disk utilization percentage they report does include
seek time, not just read/write operations.
NetApp has been involved in trying to figure out what is going on and
their claim is that the NetApp filer is not IO bound.
>
> You did not say what sort of query this is, but I gather that it's
> doing
> an indexscan on a table that is not at all in index order.
Yes, most of those queries are doing an indexscan. It's a fresh
restore of our production database that we have vacuumed/analyzed.
> Possible
> solutions involve reverting to a seqscan (have you forced the planner
> to
> choose an indexscan here, either directly or by lowering
> random_page_cost?)
No.
> or CLUSTERing the table by the index (which would need to be repeated
> periodically, so it's not a great answer).
Will try to cluster the tables and see if it changes anything. Still
doesn't explain what is going on with those seeks.
Thanks,
Rémy
>
> regards, tom lane
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
@ 2005-08-30 16:25 ` Michael Stone <mstone+postgres@mathom.us>
3 siblings, 0 replies; 12+ messages in thread
From: Michael Stone @ 2005-08-30 16:25 UTC (permalink / raw)
To: pgsql-performance
On Mon, Aug 29, 2005 at 09:42:46AM -0400, Rémy Beaumont wrote:
>We have been trying to pinpoint what originally seem to be a I/O
>bottleneck but which now seems to be an issue with either Postgresql or
>RHES 3.
Nope, it's an IO bottleneck.
>The behavior we see is that when running queries that do random reads
>on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
>throughput bellow 3000kB/s
That's the sign of an IO bottleneck.
>The stats of the NetApp do confirm that it is sitting idle. Doing an
>strace on the Postgresql process shows that is it doing seeks and
>reads.
>
>So my question is where is this iowait time spent ?
Waiting for the seeks. postgres doesn't do async io, so it requests a
block, waits for it to come in, then requests another block, etc. The
utilization on the netapp isn't going to be high because it doesn't have
a queue of requests and can't do readahead because the IO is random. The
only way to improve the situation would be to reduce the latency of the
seeks. If I read the numbers right you're only getting about 130
seeks/s, which ain't great. I don't know how much latency the netapp
adds in the this configuration; have you tried benchmarking
direct-attach disks?
Mike Stone
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
@ 2005-08-30 18:30 ` Woody Woodring <george.woodring@iglass.net>
3 siblings, 0 replies; 12+ messages in thread
From: Woody Woodring @ 2005-08-30 18:30 UTC (permalink / raw)
To: 'Rémy Beaumont' <remyb@medrium.com>; pgsql-performance
Have you tried a different kernel? We run with a netapp over NFS without
any issues, but we have seen high IO-wait on other Dell boxes (running and
not running postgres) and RHES 3. We have replaced a Dell PowerEdge 350
running RH 7.3 with a PE750 with more memory running RHES3 and it be bogged
down with IO waits due to syslog messages writing to the disk, the old
slower server could handle it fine. I don't know if it is a Dell thing or a
RH kernel, but we try different kernels on our boxes to try to find one that
works better. We have not found one that stands out over another
consistently but we have been moving away from Update 2 kernel
(2.4.21-15.ELsmp) due to server lockup issues. Unfortunately we get the
best disk throughput on our few remaining 7.3 boxes.
Woody
IGLASS Networks
www.iglass.net
_____
From: pgsql-performance-owner@postgresql.org
[mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Rémy Beaumont
Sent: Monday, August 29, 2005 9:43 AM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] High load and iowait but no disk access
We have been trying to pinpoint what originally seem to be a I/O bottleneck
but which now seems to be an issue with either Postgresql or RHES 3.
We have the following test environment on which we can reproduce the
problem:
1) Test System A
Dell 6650 Quad Xeon Pentium 4
8 Gig of RAM
OS: RHES 3 update 2
Storage: NetApp FAS270 connected using an FC card using 10 disks
2) Test System B
Dell Dual Xeon Pentium III
2 Gig o RAM
OS: RHES 3 update 2
Storage: NetApp FAS920 connected using an FC card using 28 disks
Our Database size is around 30G.
The behavior we see is that when running queries that do random reads on
disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000 kB/s on
sequential read operations on the netapps)
The stats of the NetApp do confirm that it is sitting idle. Doing an strace
on the Postgresql process shows that is it doing seeks and reads.
So my question is where is this iowait time spent ?
Is there a way to pinpoint the problem in more details ?
We are able to reproduce this behavior with Postgresql 7.4.8 and 8.0.3
I have included the output of top,vmstat,strace and systat from the Netapp
from System B while running a single query that generates this behavior.
Rémy
top output:
06:27:28 up 5 days, 16:59, 6 users, load average: 1.04, 1.30, 1.01
72 processes: 71 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 2.7% 0.0% 1.0% 0.1% 0.2% 46.0% 49.5%
cpu00 0.2% 0.0% 0.2% 0.0% 0.2% 2.2% 97.2%
cpu01 5.3% 0.0% 1.9% 0.3% 0.3% 89.8% 1.9%
Mem: 2061696k av, 2043936k used, 17760k free, 0k shrd, 3916k buff
1566332k actv, 296648k in_d, 30504k in_c
Swap: 16771584k av, 21552k used, 16750032k free 1933772k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
30960 postgres 15 0 13424 10M 9908 D 2.7 0.5 2:00 1 postmaster
30538 root 15 0 1080 764 524 S 0.7 0.0 0:43 0 sshd
1 root 15 0 496 456 436 S 0.0 0.0 0:08 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
4 root 15 0 0 0 0 SW 0.0 0.0 0:01 0 keventd
5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
9 root 15 0 0 0 0 SW 0.0 0.0 0:24 1 bdflush
7 root 15 0 0 0 0 SW 0.0 0.0 6:53 1 kswapd
8 root 15 0 0 0 0 SW 0.0 0.0 8:44 1 kscand
10 root 15 0 0 0 0 SW 0.0 0.0 0:13 0 kupdated
11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 mdrecoveryd
17 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 ahc_dv_0
vmstat output
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy id wa
0 1 21552 17796 4872 1931928 2 3 3 1 27 6 2 1 7 3
0 1 21552 18044 4880 1931652 0 0 1652 0 397 512 1 2 50 47
0 1 21552 17976 4896 1931664 0 0 2468 0 407 552 2 2 50 47
1 0 21552 17984 4896 1931608 0 0 2124 0 418 538 3 3 48 46
0 1 21552 18028 4900 1931536 0 0 1592 0 385 509 1 3 50 46
0 1 21552 18040 4916 1931488 0 0 1620 820 419 581 2 2 50 46
0 1 21552 17968 4916 1931536 0 4 1708 4 402 554 3 1 50 46
1 1 21552 18052 4916 1931388 0 0 1772 0 409 531 3 1 49 47
0 1 21552 17912 4924 1931492 0 0 1772 0 408 565 3 1 48 48
0 1 21552 17932 4932 1931440 0 4 1356 4 391 545 5 0 49 46
0 1 21552 18320 4944 1931016 0 4 1500 840 414 571 1 1 48 50
0 1 21552 17872 4944 1931440 0 0 2116 0 392 496 1 5 46 48
0 1 21552 18060 4944 1931232 0 0 2232 0 423 597 1 2 48 49
1 1 21552 17684 4944 1931584 0 0 1752 0 395 537 1 1 50 48
0 1 21552 18000 4944 1931240 0 0 1576 0 401 549 0 1 50 49
NetApp stats:
CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s Cache Cache CP CP Disk
DAFS FCP iSCSI FCP kB/s
in out read write read write age hit time ty util in out
2% 0 0 0 139 0 0 2788 0 0 0 3 96% 0% - 15% 0 139 0 3 2277
2% 0 0 0 144 0 0 2504 0 0 0 3 96% 0% - 18% 0 144 0 3 2150
2% 0 0 0 130 0 0 2212 0 0 0 3 96% 0% - 13% 0 130 0 3 1879
3% 0 0 0 169 0 0 2937 80 0 0 3 96% 0% - 13% 0 169 0 4 2718
2% 0 0 0 139 0 0 2448 0 0 0 3 96% 0% - 12% 0 139 0 3 2096
2% 0 0 0 137 0 0 2116 0 0 0 3 96% 0% - 10% 0 137 0 3 1892
3% 0 0 0 107 0 0 2660 812 0 0 3 96% 24% T 20% 0 107 0 3 1739
2% 0 0 0 118 0 0 1788 0 0 0 3 96% 0% - 13% 0 118 0 3 1608
2% 0 0 0 136 0 0 2228 0 0 0 3 96% 0% - 11% 0 136 0 3 2018
2% 0 0 0 119 0 0 1940 0 0 0 3 96% 0% - 13% 0 119 0 3 1998
2% 0 0 0 136 0 0 2175 0 0 0 3 96% 0% - 14% 0 136 0 3 1929
2% 0 0 0 133 0 0 1924 0 0 0 3 96% 0% - 19% 0 133 0 3 2292
2% 0 0 0 115 0 0 2044 0 0 0 3 96% 0% - 11% 0 115 0 3 1682
2% 0 0 0 134 0 0 2256 0 0 0 3 96% 0% - 12% 0 134 0 3 2096
2% 0 0 0 112 0 0 2184 0 0 0 3 96% 0% - 12% 0 112 0 3 1633
2% 0 0 0 163 0 0 2348 0 0 0 3 96% 0% - 13% 0 163 0 4 2421
2% 0 0 0 120 0 0 2056 184 0 0 3 96% 8% T 14% 0 120 0 3 1703
strace output:
read(55, "\4\0\0\0\10fm}\1\0\0\0p\0\264\0\0 \2 \230\236\320\0020"..., 8192)
= 8192
_llseek(55, 857997312, [857997312], SEEK_SET) = 0
read(55, "\4\0\0\0\\\315\321|\1\0\0\0p\0\354\0\0 \2 \250\236\260"..., 8192)
= 8192
_llseek(55, 883220480, [883220480], SEEK_SET) = 0
read(55, "\4\0\0\0T\17a~\1\0\0\0p\0\20\1\0 \2 \270\236\220\2D\235"..., 8192)
= 8192
_llseek(55, 858005504, [858005504], SEEK_SET) = 0
read(55, "\4\0\0\0\300\356\321|\1\0\0\0p\0\330\0\0 \2 \260\236\240"...,
8192) = 8192
_llseek(55, 857964544, [857964544], SEEK_SET) = 0
read(55, "\4\0\0\0lH\321|\1\0\0\0p\0<\1\0 \2 \300\236\200\2p\235"..., 8192)
= 8192
_llseek(55, 857956352, [857956352], SEEK_SET) = 0
read(55, "\4\0\0\0l\'\321|\1\0\0\0p\0\320\0\0 \2 \260\236\240\2\\"..., 8192)
= 8192
_llseek(55, 910802944, [910802944], SEEK_SET) = 0
read(55, "\4\0\0\0\10}\25\200\1\0\0\0l\0\274\1\0 \2 \250\236\260"..., 8192)
= 8192
_llseek(55, 857948160, [857948160], SEEK_SET) = 0
read(55, "\4\0\0\0\370\5\321|\1\0\0\0p\0\350\0\0 \2 \230\236\320"..., 8192)
= 8192
_llseek(56, 80371712, [80371712], SEEK_SET) = 0
read(56, "\4\0\0\0Lf \217\1\0\0\0p\0\f\1\0 \2 \250\236\260\2T\235"..., 8192)
= 8192
read(102, "\2\0\34\0001\236\0\0\1\0\0\0\t\0\0\00020670\0\0\0B\6\0"..., 8192)
= 8192
_llseek(55, 857939968, [857939968], SEEK_SET) = 0
read(55, "\4\0\0\0\244\344\320|\1\0\0\0l\0\230\1\0 \2 \244\236\270"...,
8192) = 8192
_llseek(55, 857923584, [857923584], SEEK_SET) = 0
read(55, "\4\0\0\0\224\242\320|\1\0\0\0p\0|\0\0 \2 \234\236\310\002"...,
8192) = 8192
_llseek(55, 57270272, [57270272], SEEK_SET) = 0
read(55, "\4\0\0\0\3204FK\1\0\0\0t\0\340\0\0 \2 \310\236j\2\214\235"...,
8192) = 8192
_llseek(55, 870727680, [870727680], SEEK_SET) = 0
read(55, "\4\0\0\0x>\233}\1\0\0\0p\0@\1\0 \2 \250\236\260\2X\235"..., 8192)
= 8192
_llseek(55, 1014734848, [1014734848], SEEK_SET) = 0
read(55, "\4\0\0\0\34\354\201\206\1\0\0\0p\0p\0\0 \2 \264\236\230"..., 8192)
= 8192
_llseek(55, 857874432, [857874432], SEEK_SET) = 0
read(55, "\4\0\0\0\214\331\317|\1\0\0\0l\0\324\1\0 \2 \224\236\330"...,
8192) = 8192
_llseek(55, 760872960, [760872960], SEEK_SET) = 0
read(55, "\4\0\0\0\30\257\321v\1\0\0\0p\0\230\0\0 \2 \234\236\310"..., 8192)
= 8192
_llseek(55, 891715584, [891715584], SEEK_SET) = 0
read(55, "\4\0\0\0\370\220\347~\1\0\0\0p\0P\1\0 \2 \230\236\320\2"..., 8192)
= 8192
_llseek(55, 857858048, [857858048], SEEK_SET) = 0
read(55, "\4\0\0\0\250\227\317|\1\0\0\0p\0\264\0\0 \2 \254\236\250"...,
8192) = 8192
_llseek(55, 666910720, [666910720], SEEK_SET) = 0
read(55, "\4\0\0\0x\206\3q\1\0\0\0p\0004\1\0 \2 \254\236\242\2P\235"...,
8192) = 8192
_llseek(55, 857841664, [857841664], SEEK_SET) = 0
read(55, "\4\0\0\0dT\317|\1\0\0\0p\0\224\0\0 \2 \214\236\350\2\30"..., 8192)
= 8192
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
@ 2005-08-30 18:32 ` Josh Berkus <josh@agliodbs.com>
2005-08-30 18:42 ` Re: High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
3 siblings, 1 reply; 12+ messages in thread
From: Josh Berkus @ 2005-08-30 18:32 UTC (permalink / raw)
To: pgsql-performance; +Cc: Rémy Beaumont <remyb@medrium.com>
Remy,
> The behavior we see is that when running queries that do random reads
> on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
> throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000 kB/s
> on sequential read operations on the netapps)
This seems pretty low for a NetApp -- you should be able to manage up to
180mb/s, if not higher. Are you sure it's configured correctly?
--
--Josh
Josh Berkus
Aglio Database Solutions
San Francisco
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 18:32 ` Re: High load and iowait but no disk access Josh Berkus <josh@agliodbs.com>
@ 2005-08-30 18:42 ` Rémy Beaumont <remyb@medrium.com>
0 siblings, 0 replies; 12+ messages in thread
From: Rémy Beaumont @ 2005-08-30 18:42 UTC (permalink / raw)
To: josh@agliodbs.com; +Cc: pgsql-performance
On 30-Aug-05, at 14:32, Josh Berkus wrote:
> Remy,
>
>> The behavior we see is that when running queries that do random reads
>> on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
>> throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000
>> kB/s
>> on sequential read operations on the netapps)
>
> This seems pretty low for a NetApp -- you should be able to manage up
> to
> 180mb/s, if not higher. Are you sure it's configured correctly?
Hi Josh,
The config has been reviewed by NetApp. We do get rates higher then
80mb/s, but on average, that's what we get.
Do you have NetApp filers deployed ?
How many spindles do you have in your volume ?
On which OS are you running Postgres ?
Thanks,
Rémy
>
> --
> --Josh
>
> Josh Berkus
> Aglio Database Solutions
> San Francisco
>
> ---------------------------(end of
> broadcast)---------------------------
> TIP 9: In versions below 8.0, the planner will ignore your desire to
> choose an index scan if your joining column's datatypes do not
> match
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
@ 2005-08-30 18:46 Anjan Dave <adave@vantage.com>
2005-08-30 18:50 ` Re: High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 19:34 ` Re: High load and iowait but no disk access mudfoot@rawbw.com
0 siblings, 2 replies; 12+ messages in thread
From: Anjan Dave @ 2005-08-30 18:46 UTC (permalink / raw)
To: Woody Woodring <george.woodring@iglass.net>; Rémy Beaumont <remyb@medrium.com>; pgsql-performance
I have seen references of changing the kernel io scheduler at boot time...not sure if it applies to RHEL3.0, or will help, but try setting 'elevator=deadline' during boot time or via grub.conf. Have you tried running a simple 'dd' on the LUN? The drives are in RAID10 configuration, right?
Thanks,
Anjan
_____
From: Woody Woodring [mailto:george.woodring@iglass.net]
Sent: Tuesday, August 30, 2005 2:30 PM
To: 'Rémy Beaumont'; pgsql-performance@postgresql.org
Subject: Re: [PERFORM] High load and iowait but no disk access
Have you tried a different kernel? We run with a netapp over NFS without any issues, but we have seen high IO-wait on other Dell boxes (running and not running postgres) and RHES 3. We have replaced a Dell PowerEdge 350 running RH 7.3 with a PE750 with more memory running RHES3 and it be bogged down with IO waits due to syslog messages writing to the disk, the old slower server could handle it fine. I don't know if it is a Dell thing or a RH kernel, but we try different kernels on our boxes to try to find one that works better. We have not found one that stands out over another consistently but we have been moving away from Update 2 kernel (2.4.21-15.ELsmp) due to server lockup issues. Unfortunately we get the best disk throughput on our few remaining 7.3 boxes.
Woody
IGLASS Networks
www.iglass.net
_____
From: pgsql-performance-owner@postgresql.org [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Rémy Beaumont
Sent: Monday, August 29, 2005 9:43 AM
To: pgsql-performance@postgresql.org
Subject: [PERFORM] High load and iowait but no disk access
We have been trying to pinpoint what originally seem to be a I/O bottleneck but which now seems to be an issue with either Postgresql or RHES 3.
We have the following test environment on which we can reproduce the problem:
1) Test System A
Dell 6650 Quad Xeon Pentium 4
8 Gig of RAM
OS: RHES 3 update 2
Storage: NetApp FAS270 connected using an FC card using 10 disks
2) Test System B
Dell Dual Xeon Pentium III
2 Gig o RAM
OS: RHES 3 update 2
Storage: NetApp FAS920 connected using an FC card using 28 disks
Our Database size is around 30G.
The behavior we see is that when running queries that do random reads on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000 kB/s on sequential read operations on the netapps)
The stats of the NetApp do confirm that it is sitting idle. Doing an strace on the Postgresql process shows that is it doing seeks and reads.
So my question is where is this iowait time spent ?
Is there a way to pinpoint the problem in more details ?
We are able to reproduce this behavior with Postgresql 7.4.8 and 8.0.3
I have included the output of top,vmstat,strace and systat from the Netapp from System B while running a single query that generates this behavior.
Rémy
top output:
06:27:28 up 5 days, 16:59, 6 users, load average: 1.04, 1.30, 1.01
72 processes: 71 sleeping, 1 running, 0 zombie, 0 stopped
CPU states: cpu user nice system irq softirq iowait idle
total 2.7% 0.0% 1.0% 0.1% 0.2% 46.0% 49.5%
cpu00 0.2% 0.0% 0.2% 0.0% 0.2% 2.2% 97.2%
cpu01 5.3% 0.0% 1.9% 0.3% 0.3% 89.8% 1.9%
Mem: 2061696k av, 2043936k used, 17760k free, 0k shrd, 3916k buff
1566332k actv, 296648k in_d, 30504k in_c
Swap: 16771584k av, 21552k used, 16750032k free 1933772k cached
PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
30960 postgres 15 0 13424 10M 9908 D 2.7 0.5 2:00 1 postmaster
30538 root 15 0 1080 764 524 S 0.7 0.0 0:43 0 sshd
1 root 15 0 496 456 436 S 0.0 0.0 0:08 0 init
2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
4 root 15 0 0 0 0 SW 0.0 0.0 0:01 0 keventd
5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
9 root 15 0 0 0 0 SW 0.0 0.0 0:24 1 bdflush
7 root 15 0 0 0 0 SW 0.0 0.0 6:53 1 kswapd
8 root 15 0 0 0 0 SW 0.0 0.0 8:44 1 kscand
10 root 15 0 0 0 0 SW 0.0 0.0 0:13 0 kupdated
11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 mdrecoveryd
17 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 ahc_dv_0
vmstat output
procs memory swap io system cpu
r b swpd free buff cache si so bi bo in cs us sy id wa
0 1 21552 17796 4872 1931928 2 3 3 1 27 6 2 1 7 3
0 1 21552 18044 4880 1931652 0 0 1652 0 397 512 1 2 50 47
0 1 21552 17976 4896 1931664 0 0 2468 0 407 552 2 2 50 47
1 0 21552 17984 4896 1931608 0 0 2124 0 418 538 3 3 48 46
0 1 21552 18028 4900 1931536 0 0 1592 0 385 509 1 3 50 46
0 1 21552 18040 4916 1931488 0 0 1620 820 419 581 2 2 50 46
0 1 21552 17968 4916 1931536 0 4 1708 4 402 554 3 1 50 46
1 1 21552 18052 4916 1931388 0 0 1772 0 409 531 3 1 49 47
0 1 21552 17912 4924 1931492 0 0 1772 0 408 565 3 1 48 48
0 1 21552 17932 4932 1931440 0 4 1356 4 391 545 5 0 49 46
0 1 21552 18320 4944 1931016 0 4 1500 840 414 571 1 1 48 50
0 1 21552 17872 4944 1931440 0 0 2116 0 392 496 1 5 46 48
0 1 21552 18060 4944 1931232 0 0 2232 0 423 597 1 2 48 49
1 1 21552 17684 4944 1931584 0 0 1752 0 395 537 1 1 50 48
0 1 21552 18000 4944 1931240 0 0 1576 0 401 549 0 1 50 49
NetApp stats:
CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s Cache Cache CP CP Disk DAFS FCP iSCSI FCP kB/s
in out read write read write age hit time ty util in out
2% 0 0 0 139 0 0 2788 0 0 0 3 96% 0% - 15% 0 139 0 3 2277
2% 0 0 0 144 0 0 2504 0 0 0 3 96% 0% - 18% 0 144 0 3 2150
2% 0 0 0 130 0 0 2212 0 0 0 3 96% 0% - 13% 0 130 0 3 1879
3% 0 0 0 169 0 0 2937 80 0 0 3 96% 0% - 13% 0 169 0 4 2718
2% 0 0 0 139 0 0 2448 0 0 0 3 96% 0% - 12% 0 139 0 3 2096
2% 0 0 0 137 0 0 2116 0 0 0 3 96% 0% - 10% 0 137 0 3 1892
3% 0 0 0 107 0 0 2660 812 0 0 3 96% 24% T 20% 0 107 0 3 1739
2% 0 0 0 118 0 0 1788 0 0 0 3 96% 0% - 13% 0 118 0 3 1608
2% 0 0 0 136 0 0 2228 0 0 0 3 96% 0% - 11% 0 136 0 3 2018
2% 0 0 0 119 0 0 1940 0 0 0 3 96% 0% - 13% 0 119 0 3 1998
2% 0 0 0 136 0 0 2175 0 0 0 3 96% 0% - 14% 0 136 0 3 1929
2% 0 0 0 133 0 0 1924 0 0 0 3 96% 0% - 19% 0 133 0 3 2292
2% 0 0 0 115 0 0 2044 0 0 0 3 96% 0% - 11% 0 115 0 3 1682
2% 0 0 0 134 0 0 2256 0 0 0 3 96% 0% - 12% 0 134 0 3 2096
2% 0 0 0 112 0 0 2184 0 0 0 3 96% 0% - 12% 0 112 0 3 1633
2% 0 0 0 163 0 0 2348 0 0 0 3 96% 0% - 13% 0 163 0 4 2421
2% 0 0 0 120 0 0 2056 184 0 0 3 96% 8% T 14% 0 120 0 3 1703
strace output:
read(55, "\4\0\0\0\10fm}\1\0\0\0p\0\264\0\0 \2 \230\236\320\0020"..., 8192) = 8192
_llseek(55, 857997312, [857997312], SEEK_SET) = 0
read(55, "\4\0\0\0\\\315\321|\1\0\0\0p\0\354\0\0 \2 \250\236\260"..., 8192) = 8192
_llseek(55, 883220480, [883220480], SEEK_SET) = 0
read(55, "\4\0\0\0T\17a~\1\0\0\0p\0\20\1\0 \2 \270\236\220\2D\235"..., 8192) = 8192
_llseek(55, 858005504, [858005504], SEEK_SET) = 0
read(55, "\4\0\0\0\300\356\321|\1\0\0\0p\0\330\0\0 \2 \260\236\240"..., 8192) = 8192
_llseek(55, 857964544, [857964544], SEEK_SET) = 0
read(55, "\4\0\0\0lH\321|\1\0\0\0p\0<\1\0 \2 \300\236\200\2p\235"..., 8192) = 8192
_llseek(55, 857956352, [857956352], SEEK_SET) = 0
read(55, "\4\0\0\0l\'\321|\1\0\0\0p\0\320\0\0 \2 \260\236\240\2\\"..., 8192) = 8192
_llseek(55, 910802944, [910802944], SEEK_SET) = 0
read(55, "\4\0\0\0\10}\25\200\1\0\0\0l\0\274\1\0 \2 \250\236\260"..., 8192) = 8192
_llseek(55, 857948160, [857948160], SEEK_SET) = 0
read(55, "\4\0\0\0\370\5\321|\1\0\0\0p\0\350\0\0 \2 \230\236\320"..., 8192) = 8192
_llseek(56, 80371712, [80371712], SEEK_SET) = 0
read(56, "\4\0\0\0Lf \217\1\0\0\0p\0\f\1\0 \2 \250\236\260\2T\235"..., 8192) = 8192
read(102, "\2\0\34\0001\236\0\0\1\0\0\0\t\0\0\00020670\0\0\0B\6\0"..., 8192) = 8192
_llseek(55, 857939968, [857939968], SEEK_SET) = 0
read(55, "\4\0\0\0\244\344\320|\1\0\0\0l\0\230\1\0 \2 \244\236\270"..., 8192) = 8192
_llseek(55, 857923584, [857923584], SEEK_SET) = 0
read(55, "\4\0\0\0\224\242\320|\1\0\0\0p\0|\0\0 \2 \234\236\310\002"..., 8192) = 8192
_llseek(55, 57270272, [57270272], SEEK_SET) = 0
read(55, "\4\0\0\0\3204FK\1\0\0\0t\0\340\0\0 \2 \310\236j\2\214\235"..., 8192) = 8192
_llseek(55, 870727680, [870727680], SEEK_SET) = 0
read(55, "\4\0\0\0x>\233}\1\0\0\0p\0@\1\0 \2 \250\236\260\2X\235"..., 8192) = 8192
_llseek(55, 1014734848, [1014734848], SEEK_SET) = 0
read(55, "\4\0\0\0\34\354\201\206\1\0\0\0p\0p\0\0 \2 \264\236\230"..., 8192) = 8192
_llseek(55, 857874432, [857874432], SEEK_SET) = 0
read(55, "\4\0\0\0\214\331\317|\1\0\0\0l\0\324\1\0 \2 \224\236\330"..., 8192) = 8192
_llseek(55, 760872960, [760872960], SEEK_SET) = 0
read(55, "\4\0\0\0\30\257\321v\1\0\0\0p\0\230\0\0 \2 \234\236\310"..., 8192) = 8192
_llseek(55, 891715584, [891715584], SEEK_SET) = 0
read(55, "\4\0\0\0\370\220\347~\1\0\0\0p\0P\1\0 \2 \230\236\320\2"..., 8192) = 8192
_llseek(55, 857858048, [857858048], SEEK_SET) = 0
read(55, "\4\0\0\0\250\227\317|\1\0\0\0p\0\264\0\0 \2 \254\236\250"..., 8192) = 8192
_llseek(55, 666910720, [666910720], SEEK_SET) = 0
read(55, "\4\0\0\0x\206\3q\1\0\0\0p\0004\1\0 \2 \254\236\242\2P\235"..., 8192) = 8192
_llseek(55, 857841664, [857841664], SEEK_SET) = 0
read(55, "\4\0\0\0dT\317|\1\0\0\0p\0\224\0\0 \2 \214\236\350\2\30"..., 8192) = 8192
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-30 18:46 Re: High load and iowait but no disk access Anjan Dave <adave@vantage.com>
@ 2005-08-30 18:50 ` Rémy Beaumont <remyb@medrium.com>
1 sibling, 0 replies; 12+ messages in thread
From: Rémy Beaumont @ 2005-08-30 18:50 UTC (permalink / raw)
To: Anjan Dave <adave@vantage.com>; +Cc: pgsql-performance; pgsql-performance
On 30-Aug-05, at 14:46, Anjan Dave wrote:
> I have seen references of changing the kernel io scheduler at boot
> time…not sure if it applies to RHEL3.0, or will help, but try setting
> ‘elevator=deadline’ during boot time or via grub.conf.
That's only for RHEL 4.0.
> Have you tried running a simple ‘dd’ on the LUN?
We get amazing performance using dd.
> The drives are in RAID10 configuration, right?
NetApp has their own type of raid format (RAID4 aka WAFL)
Rémy
>
> Thanks,
> Anjan
>
> From: Woody Woodring [mailto:george.woodring@iglass.net]
> Sent: Tuesday, August 30, 2005 2:30 PM
> To: 'Rémy Beaumont'; pgsql-performance@postgresql.org
> Subject: Re: [PERFORM] High load and iowait but no disk access
>
> Have you tried a different kernel? We run with a netapp over NFS
> without any issues, but we have seen high IO-wait on other Dell boxes
> (running and not running postgres) and RHES 3. We have replaced a
> Dell PowerEdge 350 running RH 7.3 with a PE750 with more memory
> running RHES3 and it be bogged down with IO waits due to syslog
> messages writing to the disk, the old slower server could handle it
> fine. I don't know if it is a Dell thing or a RH kernel, but we try
> different kernels on our boxes to try to find one that works better.
> We have not found one that stands out over another consistently but we
> have been moving away from Update 2 kernel (2.4.21-15.ELsmp) due to
> server lockup issues. Unfortunately we get the best disk throughput
> on our few remaining 7.3 boxes.
>
> Woody
>
> IGLASS Networks
> www.iglass.net
>
>
>
> From: pgsql-performance-owner@postgresql.org
> [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Rémy
> Beaumont
> Sent: Monday, August 29, 2005 9:43 AM
> To: pgsql-performance@postgresql.org
> Subject: [PERFORM] High load and iowait but no disk access
> We have been trying to pinpoint what originally seem to be a I/O
> bottleneck but which now seems to be an issue with either Postgresql
> or RHES 3.
>
> We have the following test environment on which we can reproduce the
> problem:
>
> 1) Test System A
> Dell 6650 Quad Xeon Pentium 4
> 8 Gig of RAM
> OS: RHES 3 update 2
> Storage: NetApp FAS270 connected using an FC card using 10 disks
>
> 2) Test System B
> Dell Dual Xeon Pentium III
> 2 Gig o RAM
> OS: RHES 3 update 2
> Storage: NetApp FAS920 connected using an FC card using 28 disks
>
> Our Database size is around 30G.
>
> The behavior we see is that when running queries that do random reads
> on disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
> throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000
> kB/s on sequential read operations on the netapps)
>
> The stats of the NetApp do confirm that it is sitting idle. Doing an
> strace on the Postgresql process shows that is it doing seeks and
> reads.
>
> So my question is where is this iowait time spent ?
> Is there a way to pinpoint the problem in more details ?
> We are able to reproduce this behavior with Postgresql 7.4.8 and 8.0.3
>
> I have included the output of top,vmstat,strace and systat from the
> Netapp from System B while running a single query that generates this
> behavior.
>
> Rémy
>
> top output:
> 06:27:28 up 5 days, 16:59, 6 users, load average: 1.04, 1.30, 1.01
> 72 processes: 71 sleeping, 1 running, 0 zombie, 0 stopped
> CPU states: cpu user nice system irq softirq iowait idle
> total 2.7% 0.0% 1.0% 0.1% 0.2% 46.0% 49.5%
> cpu00 0.2% 0.0% 0.2% 0.0% 0.2% 2.2% 97.2%
> cpu01 5.3% 0.0% 1.9% 0.3% 0.3% 89.8% 1.9%
> Mem: 2061696k av, 2043936k used, 17760k free, 0k shrd, 3916k buff
> 1566332k actv, 296648k in_d, 30504k in_c
> Swap: 16771584k av, 21552k used, 16750032k free 1933772k cached
>
> PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
> 30960 postgres 15 0 13424 10M 9908 D 2.7 0.5 2:00 1 postmaster
> 30538 root 15 0 1080 764 524 S 0.7 0.0 0:43 0 sshd
> 1 root 15 0 496 456 436 S 0.0 0.0 0:08 0 init
> 2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
> 3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
> 4 root 15 0 0 0 0 SW 0.0 0.0 0:01 0 keventd
> 5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
> 6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
> 9 root 15 0 0 0 0 SW 0.0 0.0 0:24 1 bdflush
> 7 root 15 0 0 0 0 SW 0.0 0.0 6:53 1 kswapd
> 8 root 15 0 0 0 0 SW 0.0 0.0 8:44 1 kscand
> 10 root 15 0 0 0 0 SW 0.0 0.0 0:13 0 kupdated
> 11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 mdrecoveryd
> 17 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 ahc_dv_0
>
>
> vmstat output
> procs memory swap io system cpu
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 0 1 21552 17796 4872 1931928 2 3 3 1 27 6 2 1 7 3
> 0 1 21552 18044 4880 1931652 0 0 1652 0 397 512 1 2 50 47
> 0 1 21552 17976 4896 1931664 0 0 2468 0 407 552 2 2 50 47
> 1 0 21552 17984 4896 1931608 0 0 2124 0 418 538 3 3 48 46
> 0 1 21552 18028 4900 1931536 0 0 1592 0 385 509 1 3 50 46
> 0 1 21552 18040 4916 1931488 0 0 1620 820 419 581 2 2 50 46
> 0 1 21552 17968 4916 1931536 0 4 1708 4 402 554 3 1 50 46
> 1 1 21552 18052 4916 1931388 0 0 1772 0 409 531 3 1 49 47
> 0 1 21552 17912 4924 1931492 0 0 1772 0 408 565 3 1 48 48
> 0 1 21552 17932 4932 1931440 0 4 1356 4 391 545 5 0 49 46
> 0 1 21552 18320 4944 1931016 0 4 1500 840 414 571 1 1 48 50
> 0 1 21552 17872 4944 1931440 0 0 2116 0 392 496 1 5 46 48
> 0 1 21552 18060 4944 1931232 0 0 2232 0 423 597 1 2 48 49
> 1 1 21552 17684 4944 1931584 0 0 1752 0 395 537 1 1 50 48
> 0 1 21552 18000 4944 1931240 0 0 1576 0 401 549 0 1 50 49
>
>
> NetApp stats:
> CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s Cache Cache CP
> CP Disk DAFS FCP iSCSI FCP kB/s
> in out read write read write age hit time ty util in out
> 2% 0 0 0 139 0 0 2788 0 0 0 3 96% 0% - 15% 0 139 0 3 2277
> 2% 0 0 0 144 0 0 2504 0 0 0 3 96% 0% - 18% 0 144 0 3 2150
> 2% 0 0 0 130 0 0 2212 0 0 0 3 96% 0% - 13% 0 130 0 3 1879
> 3% 0 0 0 169 0 0 2937 80 0 0 3 96% 0% - 13% 0 169 0 4 2718
> 2% 0 0 0 139 0 0 2448 0 0 0 3 96% 0% - 12% 0 139 0 3 2096
> 2% 0 0 0 137 0 0 2116 0 0 0 3 96% 0% - 10% 0 137 0 3 1892
> 3% 0 0 0 107 0 0 2660 812 0 0 3 96% 24% T 20% 0 107 0 3 1739
> 2% 0 0 0 118 0 0 1788 0 0 0 3 96% 0% - 13% 0 118 0 3 1608
> 2% 0 0 0 136 0 0 2228 0 0 0 3 96% 0% - 11% 0 136 0 3 2018
> 2% 0 0 0 119 0 0 1940 0 0 0 3 96% 0% - 13% 0 119 0 3 1998
> 2% 0 0 0 136 0 0 2175 0 0 0 3 96% 0% - 14% 0 136 0 3 1929
> 2% 0 0 0 133 0 0 1924 0 0 0 3 96% 0% - 19% 0 133 0 3 2292
> 2% 0 0 0 115 0 0 2044 0 0 0 3 96% 0% - 11% 0 115 0 3 1682
> 2% 0 0 0 134 0 0 2256 0 0 0 3 96% 0% - 12% 0 134 0 3 2096
> 2% 0 0 0 112 0 0 2184 0 0 0 3 96% 0% - 12% 0 112 0 3 1633
> 2% 0 0 0 163 0 0 2348 0 0 0 3 96% 0% - 13% 0 163 0 4 2421
> 2% 0 0 0 120 0 0 2056 184 0 0 3 96% 8% T 14% 0 120 0 3 1703
>
> strace output:
> read(55, "\4\0\0\0\10fm}\1\0\0\0p\0\264\0\0 \2 \230\236\320\0020"...,
> 8192) = 8192
> _llseek(55, 857997312, [857997312], SEEK_SET) = 0
> read(55, "\4\0\0\0\\\315\321|\1\0\0\0p\0\354\0\0 \2 \250\236\260"...,
> 8192) = 8192
> _llseek(55, 883220480, [883220480], SEEK_SET) = 0
> read(55, "\4\0\0\0T\17a~\1\0\0\0p\0\20\1\0 \2
> \270\236\220\2D\235"..., 8192) = 8192
> _llseek(55, 858005504, [858005504], SEEK_SET) = 0
> read(55, "\4\0\0\0\300\356\321|\1\0\0\0p\0\330\0\0 \2
> \260\236\240"..., 8192) = 8192
> _llseek(55, 857964544, [857964544], SEEK_SET) = 0
> read(55, "\4\0\0\0lH\321|\1\0\0\0p\0<\1\0 \2 \300\236\200\2p\235"...,
> 8192) = 8192
> _llseek(55, 857956352, [857956352], SEEK_SET) = 0
> read(55, "\4\0\0\0l\'\321|\1\0\0\0p\0\320\0\0 \2
> \260\236\240\2\\"..., 8192) = 8192
> _llseek(55, 910802944, [910802944], SEEK_SET) = 0
> read(55, "\4\0\0\0\10}\25\200\1\0\0\0l\0\274\1\0 \2 \250\236\260"...,
> 8192) = 8192
> _llseek(55, 857948160, [857948160], SEEK_SET) = 0
> read(55, "\4\0\0\0\370\5\321|\1\0\0\0p\0\350\0\0 \2 \230\236\320"...,
> 8192) = 8192
> _llseek(56, 80371712, [80371712], SEEK_SET) = 0
> read(56, "\4\0\0\0Lf \217\1\0\0\0p\0\f\1\0 \2
> \250\236\260\2T\235"..., 8192) = 8192
> read(102,
> "\2\0\34\0001\236\0\0\1\0\0\0\t\0\0\00020670\0\0\0B\6\0"..., 8192) =
> 8192
> _llseek(55, 857939968, [857939968], SEEK_SET) = 0
> read(55, "\4\0\0\0\244\344\320|\1\0\0\0l\0\230\1\0 \2
> \244\236\270"..., 8192) = 8192
> _llseek(55, 857923584, [857923584], SEEK_SET) = 0
> read(55, "\4\0\0\0\224\242\320|\1\0\0\0p\0|\0\0 \2
> \234\236\310\002"..., 8192) = 8192
> _llseek(55, 57270272, [57270272], SEEK_SET) = 0
> read(55, "\4\0\0\0\3204FK\1\0\0\0t\0\340\0\0 \2
> \310\236j\2\214\235"..., 8192) = 8192
> _llseek(55, 870727680, [870727680], SEEK_SET) = 0
> read(55, "\4\0\0\0x>\233}\1\0\0\0p\0@\1\0 \2 \250\236\260\2X\235"...,
> 8192) = 8192
> _llseek(55, 1014734848, [1014734848], SEEK_SET) = 0
> read(55, "\4\0\0\0\34\354\201\206\1\0\0\0p\0p\0\0 \2
> \264\236\230"..., 8192) = 8192
> _llseek(55, 857874432, [857874432], SEEK_SET) = 0
> read(55, "\4\0\0\0\214\331\317|\1\0\0\0l\0\324\1\0 \2
> \224\236\330"..., 8192) = 8192
> _llseek(55, 760872960, [760872960], SEEK_SET) = 0
> read(55, "\4\0\0\0\30\257\321v\1\0\0\0p\0\230\0\0 \2
> \234\236\310"..., 8192) = 8192
> _llseek(55, 891715584, [891715584], SEEK_SET) = 0
> read(55, "\4\0\0\0\370\220\347~\1\0\0\0p\0P\1\0 \2
> \230\236\320\2"..., 8192) = 8192
> _llseek(55, 857858048, [857858048], SEEK_SET) = 0
> read(55, "\4\0\0\0\250\227\317|\1\0\0\0p\0\264\0\0 \2
> \254\236\250"..., 8192) = 8192
> _llseek(55, 666910720, [666910720], SEEK_SET) = 0
> read(55, "\4\0\0\0x\206\3q\1\0\0\0p\0004\1\0 \2
> \254\236\242\2P\235"..., 8192) = 8192
> _llseek(55, 857841664, [857841664], SEEK_SET) = 0
> read(55, "\4\0\0\0dT\317|\1\0\0\0p\0\224\0\0 \2
> \214\236\350\2\30"..., 8192) = 8192
>
>
>
^ permalink raw reply [nested|flat] 12+ messages in thread
* Re: High load and iowait but no disk access
2005-08-30 18:46 Re: High load and iowait but no disk access Anjan Dave <adave@vantage.com>
@ 2005-08-30 19:34 ` mudfoot@rawbw.com
1 sibling, 0 replies; 12+ messages in thread
From: mudfoot@rawbw.com @ 2005-08-30 19:34 UTC (permalink / raw)
To: pgsql-performance
This might be optimal behavior from the hardware. Random reads are hard to
optimize for--except if you have enough physical memory to hold the entire
dataset. Cached reads (either in array controller or OS buffer cache) should
return nearly immediately. But random reads probably aren't cached. And any
read-ahead alogorithms or other types of performance enhancements in the
hardware or OS go out the window--because the behavior isn't predictable.
Each time a drive spindle needs to move to a new track, it requires at least a
couple of miliseconds. Sequential reads only require this movement
infrequently. But random reads may be forcing this movement for every IO operation.
Since the bottleneck in random reads is the physical hard drives themselves,
everything else stands around waiting. Fancy hardware can optimize everything
else -- writes with write cache, sequential reads with read-ahead and read
cache. But there's no real solution to a purely random read workload except
perhaps creating different disk groups to help avoid spindle contention.
I like this tool: http://www.soliddata.com/products/iotest.html
It allows you to select pure workloads (read/write/sequential/random), and it
runs against raw devices, so you bypass the OS buffer cache. When I've run it
I've always seen sequential activity get much much higher throughput than random.
Quoting Anjan Dave <adave@vantage.com>:
> I have seen references of changing the kernel io scheduler at boot time...not
> sure if it applies to RHEL3.0, or will help, but try setting
> 'elevator=deadline' during boot time or via grub.conf. Have you tried running
> a simple 'dd' on the LUN? The drives are in RAID10 configuration, right?
>
>
>
> Thanks,
>
> Anjan
>
> _____
>
> From: Woody Woodring [mailto:george.woodring@iglass.net]
> Sent: Tuesday, August 30, 2005 2:30 PM
> To: 'Rémy Beaumont'; pgsql-performance@postgresql.org
> Subject: Re: [PERFORM] High load and iowait but no disk access
>
>
>
> Have you tried a different kernel? We run with a netapp over NFS without any
> issues, but we have seen high IO-wait on other Dell boxes (running and not
> running postgres) and RHES 3. We have replaced a Dell PowerEdge 350 running
> RH 7.3 with a PE750 with more memory running RHES3 and it be bogged down
> with IO waits due to syslog messages writing to the disk, the old slower
> server could handle it fine. I don't know if it is a Dell thing or a RH
> kernel, but we try different kernels on our boxes to try to find one that
> works better. We have not found one that stands out over another
> consistently but we have been moving away from Update 2 kernel
> (2.4.21-15.ELsmp) due to server lockup issues. Unfortunately we get the best
> disk throughput on our few remaining 7.3 boxes.
>
>
>
> Woody
>
>
>
> IGLASS Networks
>
> www.iglass.net
>
>
>
> _____
>
> From: pgsql-performance-owner@postgresql.org
> [mailto:pgsql-performance-owner@postgresql.org] On Behalf Of Rémy Beaumont
> Sent: Monday, August 29, 2005 9:43 AM
> To: pgsql-performance@postgresql.org
> Subject: [PERFORM] High load and iowait but no disk access
>
> We have been trying to pinpoint what originally seem to be a I/O bottleneck
> but which now seems to be an issue with either Postgresql or RHES 3.
>
> We have the following test environment on which we can reproduce the
> problem:
>
> 1) Test System A
> Dell 6650 Quad Xeon Pentium 4
> 8 Gig of RAM
> OS: RHES 3 update 2
> Storage: NetApp FAS270 connected using an FC card using 10 disks
>
> 2) Test System B
> Dell Dual Xeon Pentium III
> 2 Gig o RAM
> OS: RHES 3 update 2
> Storage: NetApp FAS920 connected using an FC card using 28 disks
>
> Our Database size is around 30G.
>
> The behavior we see is that when running queries that do random reads on
> disk, IOWAIT goes over 80% and actual disk IO falls to a crawl at a
> throughput bellow 3000kB/s (We usually average 40000 kB/s to 80000 kB/s on
> sequential read operations on the netapps)
>
> The stats of the NetApp do confirm that it is sitting idle. Doing an strace
> on the Postgresql process shows that is it doing seeks and reads.
>
> So my question is where is this iowait time spent ?
> Is there a way to pinpoint the problem in more details ?
> We are able to reproduce this behavior with Postgresql 7.4.8 and 8.0.3
>
> I have included the output of top,vmstat,strace and systat from the Netapp
> from System B while running a single query that generates this behavior.
>
> Rémy
>
> top output:
> 06:27:28 up 5 days, 16:59, 6 users, load average: 1.04, 1.30, 1.01
> 72 processes: 71 sleeping, 1 running, 0 zombie, 0 stopped
> CPU states: cpu user nice system irq softirq iowait idle
> total 2.7% 0.0% 1.0% 0.1% 0.2% 46.0% 49.5%
> cpu00 0.2% 0.0% 0.2% 0.0% 0.2% 2.2% 97.2%
> cpu01 5.3% 0.0% 1.9% 0.3% 0.3% 89.8% 1.9%
> Mem: 2061696k av, 2043936k used, 17760k free, 0k shrd, 3916k buff
> 1566332k actv, 296648k in_d, 30504k in_c
> Swap: 16771584k av, 21552k used, 16750032k free 1933772k cached
>
> PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU COMMAND
> 30960 postgres 15 0 13424 10M 9908 D 2.7 0.5 2:00 1 postmaster
> 30538 root 15 0 1080 764 524 S 0.7 0.0 0:43 0 sshd
> 1 root 15 0 496 456 436 S 0.0 0.0 0:08 0 init
> 2 root RT 0 0 0 0 SW 0.0 0.0 0:00 0 migration/0
> 3 root RT 0 0 0 0 SW 0.0 0.0 0:00 1 migration/1
> 4 root 15 0 0 0 0 SW 0.0 0.0 0:01 0 keventd
> 5 root 34 19 0 0 0 SWN 0.0 0.0 0:00 0 ksoftirqd/0
> 6 root 34 19 0 0 0 SWN 0.0 0.0 0:00 1 ksoftirqd/1
> 9 root 15 0 0 0 0 SW 0.0 0.0 0:24 1 bdflush
> 7 root 15 0 0 0 0 SW 0.0 0.0 6:53 1 kswapd
> 8 root 15 0 0 0 0 SW 0.0 0.0 8:44 1 kscand
> 10 root 15 0 0 0 0 SW 0.0 0.0 0:13 0 kupdated
> 11 root 25 0 0 0 0 SW 0.0 0.0 0:00 0 mdrecoveryd
> 17 root 15 0 0 0 0 SW 0.0 0.0 0:00 0 ahc_dv_0
>
>
> vmstat output
> procs memory swap io system cpu
> r b swpd free buff cache si so bi bo in cs us sy id wa
> 0 1 21552 17796 4872 1931928 2 3 3 1 27 6 2 1 7 3
> 0 1 21552 18044 4880 1931652 0 0 1652 0 397 512 1 2 50 47
> 0 1 21552 17976 4896 1931664 0 0 2468 0 407 552 2 2 50 47
> 1 0 21552 17984 4896 1931608 0 0 2124 0 418 538 3 3 48 46
> 0 1 21552 18028 4900 1931536 0 0 1592 0 385 509 1 3 50 46
> 0 1 21552 18040 4916 1931488 0 0 1620 820 419 581 2 2 50 46
> 0 1 21552 17968 4916 1931536 0 4 1708 4 402 554 3 1 50 46
> 1 1 21552 18052 4916 1931388 0 0 1772 0 409 531 3 1 49 47
> 0 1 21552 17912 4924 1931492 0 0 1772 0 408 565 3 1 48 48
> 0 1 21552 17932 4932 1931440 0 4 1356 4 391 545 5 0 49 46
> 0 1 21552 18320 4944 1931016 0 4 1500 840 414 571 1 1 48 50
> 0 1 21552 17872 4944 1931440 0 0 2116 0 392 496 1 5 46 48
> 0 1 21552 18060 4944 1931232 0 0 2232 0 423 597 1 2 48 49
> 1 1 21552 17684 4944 1931584 0 0 1752 0 395 537 1 1 50 48
> 0 1 21552 18000 4944 1931240 0 0 1576 0 401 549 0 1 50 49
>
>
> NetApp stats:
> CPU NFS CIFS HTTP Total Net kB/s Disk kB/s Tape kB/s Cache Cache CP CP Disk
> DAFS FCP iSCSI FCP kB/s
> in out read write read write age hit time ty util in out
> 2% 0 0 0 139 0 0 2788 0 0 0 3 96% 0% - 15% 0 139 0 3 2277
> 2% 0 0 0 144 0 0 2504 0 0 0 3 96% 0% - 18% 0 144 0 3 2150
> 2% 0 0 0 130 0 0 2212 0 0 0 3 96% 0% - 13% 0 130 0 3 1879
> 3% 0 0 0 169 0 0 2937 80 0 0 3 96% 0% - 13% 0 169 0 4 2718
> 2% 0 0 0 139 0 0 2448 0 0 0 3 96% 0% - 12% 0 139 0 3 2096
> 2% 0 0 0 137 0 0 2116 0 0 0 3 96% 0% - 10% 0 137 0 3 1892
> 3% 0 0 0 107 0 0 2660 812 0 0 3 96% 24% T 20% 0 107 0 3 1739
> 2% 0 0 0 118 0 0 1788 0 0 0 3 96% 0% - 13% 0 118 0 3 1608
> 2% 0 0 0 136 0 0 2228 0 0 0 3 96% 0% - 11% 0 136 0 3 2018
> 2% 0 0 0 119 0 0 1940 0 0 0 3 96% 0% - 13% 0 119 0 3 1998
> 2% 0 0 0 136 0 0 2175 0 0 0 3 96% 0% - 14% 0 136 0 3 1929
> 2% 0 0 0 133 0 0 1924 0 0 0 3 96% 0% - 19% 0 133 0 3 2292
> 2% 0 0 0 115 0 0 2044 0 0 0 3 96% 0% - 11% 0 115 0 3 1682
> 2% 0 0 0 134 0 0 2256 0 0 0 3 96% 0% - 12% 0 134 0 3 2096
> 2% 0 0 0 112 0 0 2184 0 0 0 3 96% 0% - 12% 0 112 0 3 1633
> 2% 0 0 0 163 0 0 2348 0 0 0 3 96% 0% - 13% 0 163 0 4 2421
> 2% 0 0 0 120 0 0 2056 184 0 0 3 96% 8% T 14% 0 120 0 3 1703
>
> strace output:
> read(55, "\4\0\0\0\10fm}\1\0\0\0p\0\264\0\0 \2 \230\236\320\0020"..., 8192) =
> 8192
> _llseek(55, 857997312, [857997312], SEEK_SET) = 0
> read(55, "\4\0\0\0\\\315\321|\1\0\0\0p\0\354\0\0 \2 \250\236\260"..., 8192) =
> 8192
> _llseek(55, 883220480, [883220480], SEEK_SET) = 0
> read(55, "\4\0\0\0T\17a~\1\0\0\0p\0\20\1\0 \2 \270\236\220\2D\235"..., 8192)
> = 8192
> _llseek(55, 858005504, [858005504], SEEK_SET) = 0
> read(55, "\4\0\0\0\300\356\321|\1\0\0\0p\0\330\0\0 \2 \260\236\240"..., 8192)
> = 8192
> _llseek(55, 857964544, [857964544], SEEK_SET) = 0
> read(55, "\4\0\0\0lH\321|\1\0\0\0p\0<\1\0 \2 \300\236\200\2p\235"..., 8192) =
> 8192
> _llseek(55, 857956352, [857956352], SEEK_SET) = 0
> read(55, "\4\0\0\0l\'\321|\1\0\0\0p\0\320\0\0 \2 \260\236\240\2\\"..., 8192)
> = 8192
> _llseek(55, 910802944, [910802944], SEEK_SET) = 0
> read(55, "\4\0\0\0\10}\25\200\1\0\0\0l\0\274\1\0 \2 \250\236\260"..., 8192) =
> 8192
> _llseek(55, 857948160, [857948160], SEEK_SET) = 0
> read(55, "\4\0\0\0\370\5\321|\1\0\0\0p\0\350\0\0 \2 \230\236\320"..., 8192) =
> 8192
> _llseek(56, 80371712, [80371712], SEEK_SET) = 0
> read(56, "\4\0\0\0Lf \217\1\0\0\0p\0\f\1\0 \2 \250\236\260\2T\235"..., 8192)
> = 8192
> read(102, "\2\0\34\0001\236\0\0\1\0\0\0\t\0\0\00020670\0\0\0B\6\0"..., 8192)
> = 8192
> _llseek(55, 857939968, [857939968], SEEK_SET) = 0
> read(55, "\4\0\0\0\244\344\320|\1\0\0\0l\0\230\1\0 \2 \244\236\270"..., 8192)
> = 8192
> _llseek(55, 857923584, [857923584], SEEK_SET) = 0
> read(55, "\4\0\0\0\224\242\320|\1\0\0\0p\0|\0\0 \2 \234\236\310\002"...,
> 8192) = 8192
> _llseek(55, 57270272, [57270272], SEEK_SET) = 0
> read(55, "\4\0\0\0\3204FK\1\0\0\0t\0\340\0\0 \2 \310\236j\2\214\235"...,
> 8192) = 8192
> _llseek(55, 870727680, [870727680], SEEK_SET) = 0
> read(55, "\4\0\0\0x>\233}\1\0\0\0p\0@\1\0 \2 \250\236\260\2X\235"..., 8192) =
> 8192
> _llseek(55, 1014734848, [1014734848], SEEK_SET) = 0
> read(55, "\4\0\0\0\34\354\201\206\1\0\0\0p\0p\0\0 \2 \264\236\230"..., 8192)
> = 8192
> _llseek(55, 857874432, [857874432], SEEK_SET) = 0
> read(55, "\4\0\0\0\214\331\317|\1\0\0\0l\0\324\1\0 \2 \224\236\330"..., 8192)
> = 8192
> _llseek(55, 760872960, [760872960], SEEK_SET) = 0
> read(55, "\4\0\0\0\30\257\321v\1\0\0\0p\0\230\0\0 \2 \234\236\310"..., 8192)
> = 8192
> _llseek(55, 891715584, [891715584], SEEK_SET) = 0
> read(55, "\4\0\0\0\370\220\347~\1\0\0\0p\0P\1\0 \2 \230\236\320\2"..., 8192)
> = 8192
> _llseek(55, 857858048, [857858048], SEEK_SET) = 0
> read(55, "\4\0\0\0\250\227\317|\1\0\0\0p\0\264\0\0 \2 \254\236\250"..., 8192)
> = 8192
> _llseek(55, 666910720, [666910720], SEEK_SET) = 0
> read(55, "\4\0\0\0x\206\3q\1\0\0\0p\0004\1\0 \2 \254\236\242\2P\235"...,
> 8192) = 8192
> _llseek(55, 857841664, [857841664], SEEK_SET) = 0
> read(55, "\4\0\0\0dT\317|\1\0\0\0p\0\224\0\0 \2 \214\236\350\2\30"..., 8192)
> = 8192
>
>
>
>
>
>
^ permalink raw reply [nested|flat] 12+ messages in thread
end of thread, other threads:[~2005-08-30 19:34 UTC | newest]
Thread overview: 12+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2005-08-29 13:42 High load and iowait but no disk access Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:15 ` Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:19 ` Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:29 ` Tom Lane <tgl@sss.pgh.pa.us>
2005-08-30 16:42 ` Rémy Beaumont <remyb@medrium.com>
2005-08-30 16:25 ` Michael Stone <mstone+postgres@mathom.us>
2005-08-30 18:30 ` Woody Woodring <george.woodring@iglass.net>
2005-08-30 18:32 ` Josh Berkus <josh@agliodbs.com>
2005-08-30 18:42 ` Rémy Beaumont <remyb@medrium.com>
2005-08-30 18:46 Re: High load and iowait but no disk access Anjan Dave <adave@vantage.com>
2005-08-30 18:50 ` Rémy Beaumont <remyb@medrium.com>
2005-08-30 19:34 ` mudfoot@rawbw.com
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