To: "Christopher Petrilli" <petrilli@gmail.com>,
 "Tom Lane" <tgl@sss.pgh.pa.us>
Cc: "Vivek Khera" <vivek@khera.org>, pgsql-performance@postgresql.org
Subject: Re: Impact of checkpoint_segments under continual load conditions
References: <59d991c4050717100874c08a86@mail.gmail.com>
	<A50B8A1F-71A1-4F63-A5F4-1AA58F89557D@khera.org>
	<59d991c405071811457ccdd3f1@mail.gmail.com>
	<16394.1121715156@sss.pgh.pa.us>
	<59d991c405071812342e290f57@mail.gmail.com>
	<16794.1121718743@sss.pgh.pa.us>
	<59d991c405071907482bb0689b@mail.gmail.com>
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Date: Tue, 19 Jul 2005 17:33:21 +0200
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	What happens if, say at iteration 6000 (a bit after the mess starts), you  
pause it for a few minutes and resume. Will it restart with a plateau like  
at the beginning of the test ? or not ?
	What if, during this pause, you disconnect and reconnect, or restart the  
postmaster, or vacuum, or analyze ?


> On 7/18/05, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> > The table has 15 columns, 5 indexes (character, inet and timestamp).
>> > No foreign keys. The only other thing running on the machine was the
>> > application actually DOING the benchmarking, written in Python
>> > (psycopg), but it was, according to top, using less than 1% of the
>> > CPU.  It was just talking through a pipe to a psql prompt to do the
>> > COPY.
>>
>> Sounds pretty plain-vanilla all right.
>>
>> Are you in a position to try the same benchmark against CVS tip?
>> (The nightly snapshot tarball would be plenty close enough.)  I'm
>> just wondering if the old bgwriter behavior of locking down the
>> bufmgr while it examined the ARC/2Q data structures is causing this...
>
> Tom,
>
> It looks like the CVS HEAD is definately "better," but not by a huge
> amount.  The only difference is I wasn't run autovacuum in the
> background (default settings), but I don't think this explains it.
> Here's a graph of the differences and density of behavior:
>
> http://blog.amber.org/diagrams/pgsql_copy_803_cvs.png
>
> I can provide the raw data.  Each COPY was 500 rows.  Note that fsync
> is turned off here.  Maybe it'd be more stable with it turned on?
>
> Chris