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* effective_cache_size on 32-bits postgres
@ 2013-03-18 17:53 Rodrigo Barboza <rodrigombufrj@gmail.com>
0 siblings, 2 replies; 11+ messages in thread
From: Rodrigo Barboza @ 2013-03-18 17:53 UTC (permalink / raw)
To: pgsql-performance
Hi guys, I am worried about the effective_cache_size.
I run a 32-bits postgres installation on a machine with 64 bits kernel.
Should I limit effective_cache_size to a maximum of 2.5gb?
^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:14 Rob Wultsch <wultsch@gmail.com>
parent: Rodrigo Barboza <rodrigombufrj@gmail.com>
1 sibling, 0 replies; 11+ messages in thread
From: Rob Wultsch @ 2013-03-18 18:14 UTC (permalink / raw)
To: Rodrigo Barboza <rodrigombufrj@gmail.com>; +Cc: pgsql-performance
On Mon, Mar 18, 2013 at 10:53 AM, Rodrigo Barboza
<rodrigombufrj@gmail.com> wrote:
> Hi guys, I am worried about the effective_cache_size.
> I run a 32-bits postgres installation on a machine with 64 bits kernel.
> Should I limit effective_cache_size to a maximum of 2.5gb?
That variables refers to fs cache, so 32 bit pg should not matter.
Shared buffers and similar variables will be another matter.
Why the heck are you running 32 bit pg on a 64 bit system? You are
almost certainly doing it wrong.
--
Rob Wultsch
wultsch@gmail.com
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^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:15 Pavel Stehule <pavel.stehule@gmail.com>
parent: Rodrigo Barboza <rodrigombufrj@gmail.com>
1 sibling, 2 replies; 11+ messages in thread
From: Pavel Stehule @ 2013-03-18 18:15 UTC (permalink / raw)
To: Rodrigo Barboza <rodrigombufrj@gmail.com>; +Cc: pgsql-performance
Hello
2013/3/18 Rodrigo Barboza <rodrigombufrj@gmail.com>:
> Hi guys, I am worried about the effective_cache_size.
> I run a 32-bits postgres installation on a machine with 64 bits kernel.
> Should I limit effective_cache_size to a maximum of 2.5gb?
sure and probably little bit less
Regards
Pavel
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^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:18 Rodrigo Barboza <rodrigombufrj@gmail.com>
parent: Pavel Stehule <pavel.stehule@gmail.com>
1 sibling, 0 replies; 11+ messages in thread
From: Rodrigo Barboza @ 2013-03-18 18:18 UTC (permalink / raw)
To: Pavel Stehule <pavel.stehule@gmail.com>; +Cc: pgsql-performance
Ok, now I'm lost, who is right about the limit? Rob or Pavel?
Rob, I know it should be a 64 bit, and it will be soon, but there are good
reasons for this scenario and it's ok for now.
On Mon, Mar 18, 2013 at 3:15 PM, Pavel Stehule <pavel.stehule@gmail.com>wrote:
> Hello
>
> 2013/3/18 Rodrigo Barboza <rodrigombufrj@gmail.com>:
> > Hi guys, I am worried about the effective_cache_size.
> > I run a 32-bits postgres installation on a machine with 64 bits kernel.
> > Should I limit effective_cache_size to a maximum of 2.5gb?
>
> sure and probably little bit less
>
> Regards
>
> Pavel
>
^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:18 Pavel Stehule <pavel.stehule@gmail.com>
parent: Pavel Stehule <pavel.stehule@gmail.com>
1 sibling, 1 reply; 11+ messages in thread
From: Pavel Stehule @ 2013-03-18 18:18 UTC (permalink / raw)
To: Rodrigo Barboza <rodrigombufrj@gmail.com>; +Cc: pgsql-performance
2013/3/18 Pavel Stehule <pavel.stehule@gmail.com>:
> Hello
>
> 2013/3/18 Rodrigo Barboza <rodrigombufrj@gmail.com>:
>> Hi guys, I am worried about the effective_cache_size.
>> I run a 32-bits postgres installation on a machine with 64 bits kernel.
>> Should I limit effective_cache_size to a maximum of 2.5gb?
>
> sure and probably little bit less
wrong reply - Rob has true
Pavel
>
> Regards
>
> Pavel
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^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:23 Rodrigo Barboza <rodrigombufrj@gmail.com>
parent: Pavel Stehule <pavel.stehule@gmail.com>
0 siblings, 2 replies; 11+ messages in thread
From: Rodrigo Barboza @ 2013-03-18 18:23 UTC (permalink / raw)
To: Pavel Stehule <pavel.stehule@gmail.com>; +Cc: pgsql-performance
So setting this as half of ram, as suggested in postgres tuning webpage
should be safe?
It says it is a conservative value...
On Mon, Mar 18, 2013 at 3:18 PM, Pavel Stehule <pavel.stehule@gmail.com>wrote:
> 2013/3/18 Pavel Stehule <pavel.stehule@gmail.com>:
> > Hello
> >
> > 2013/3/18 Rodrigo Barboza <rodrigombufrj@gmail.com>:
> >> Hi guys, I am worried about the effective_cache_size.
> >> I run a 32-bits postgres installation on a machine with 64 bits kernel.
> >> Should I limit effective_cache_size to a maximum of 2.5gb?
> >
> > sure and probably little bit less
>
> wrong reply - Rob has true
>
> Pavel
>
> >
> > Regards
> >
> > Pavel
>
^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:33 Pavel Stehule <pavel.stehule@gmail.com>
parent: Rodrigo Barboza <rodrigombufrj@gmail.com>
1 sibling, 0 replies; 11+ messages in thread
From: Pavel Stehule @ 2013-03-18 18:33 UTC (permalink / raw)
To: Rodrigo Barboza <rodrigombufrj@gmail.com>; +Cc: pgsql-performance
2013/3/18 Rodrigo Barboza <rodrigombufrj@gmail.com>:
> So setting this as half of ram, as suggested in postgres tuning webpage
> should be safe?
> It says it is a conservative value...
depends how much memory is used as cache ??
it can be a shared_buffers + file system cache
Regards
Pavel Stehule
>
>
> On Mon, Mar 18, 2013 at 3:18 PM, Pavel Stehule <pavel.stehule@gmail.com>
> wrote:
>>
>> 2013/3/18 Pavel Stehule <pavel.stehule@gmail.com>:
>> > Hello
>> >
>> > 2013/3/18 Rodrigo Barboza <rodrigombufrj@gmail.com>:
>> >> Hi guys, I am worried about the effective_cache_size.
>> >> I run a 32-bits postgres installation on a machine with 64 bits kernel.
>> >> Should I limit effective_cache_size to a maximum of 2.5gb?
>> >
>> > sure and probably little bit less
>>
>> wrong reply - Rob has true
>>
>> Pavel
>>
>> >
>> > Regards
>> >
>> > Pavel
>
>
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* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:47 Kevin Grittner <kgrittn@ymail.com>
parent: Rodrigo Barboza <rodrigombufrj@gmail.com>
1 sibling, 2 replies; 11+ messages in thread
From: Kevin Grittner @ 2013-03-18 18:47 UTC (permalink / raw)
To: Rodrigo Barboza <rodrigombufrj@gmail.com>; Pavel Stehule <pavel.stehule@gmail.com>; +Cc: pgsql-performance
Rodrigo Barboza <rodrigombufrj@gmail.com> wrote:
> So setting this as half of ram, as suggested in postgres tuning
> webpage should be safe?
Half of RAM is likely to be a very bad setting for any work load.
It will tend to result in the highest possible number of pages
duplicated in PostgreSQL and OS caches, reducing the cache hit
ratio. More commonly given advice is to start at 25% of RAM,
limited to 2GB on Windows or 32-bit systems or 8GB otherwise. Try
incremental adjustments from that point using your actual workload
on you actual hardware to find the "sweet spot". Some DW
environments report better performance assigning over 50% of RAM to
shared_buffers; OLTP loads often need to reduce this to prevent
periodic episodes of high latency.
--
Kevin Grittner
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:50 Pavel Stehule <pavel.stehule@gmail.com>
parent: Kevin Grittner <kgrittn@ymail.com>
1 sibling, 0 replies; 11+ messages in thread
From: Pavel Stehule @ 2013-03-18 18:50 UTC (permalink / raw)
To: Kevin Grittner <kgrittn@ymail.com>; +Cc: Rodrigo Barboza <rodrigombufrj@gmail.com>; pgsql-performance
2013/3/18 Kevin Grittner <kgrittn@ymail.com>:
> Rodrigo Barboza <rodrigombufrj@gmail.com> wrote:
>
>> So setting this as half of ram, as suggested in postgres tuning
>> webpage should be safe?
>
> Half of RAM is likely to be a very bad setting for any work load.
> It will tend to result in the highest possible number of pages
> duplicated in PostgreSQL and OS caches, reducing the cache hit
> ratio. More commonly given advice is to start at 25% of RAM,
> limited to 2GB on Windows or 32-bit systems or 8GB otherwise. Try
> incremental adjustments from that point using your actual workload
> on you actual hardware to find the "sweet spot". Some DW
> environments report better performance assigning over 50% of RAM to
> shared_buffers; OLTP loads often need to reduce this to prevent
> periodic episodes of high latency.
you are speaking about shared_buffers now.
Pavel
>
> --
> Kevin Grittner
> EnterpriseDB: http://www.enterprisedb.com
> The Enterprise PostgreSQL Company
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* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:51 Claudio Freire <klaussfreire@gmail.com>
parent: Kevin Grittner <kgrittn@ymail.com>
1 sibling, 1 reply; 11+ messages in thread
From: Claudio Freire @ 2013-03-18 18:51 UTC (permalink / raw)
To: Kevin Grittner <kgrittn@ymail.com>; +Cc: Rodrigo Barboza <rodrigombufrj@gmail.com>; Pavel Stehule <pavel.stehule@gmail.com>; pgsql-performance
On Mon, Mar 18, 2013 at 3:47 PM, Kevin Grittner <kgrittn@ymail.com> wrote:
> Rodrigo Barboza <rodrigombufrj@gmail.com> wrote:
>
>> So setting this as half of ram, as suggested in postgres tuning
>> webpage should be safe?
>
> Half of RAM is likely to be a very bad setting for any work load.
> It will tend to result in the highest possible number of pages
> duplicated in PostgreSQL and OS caches, reducing the cache hit
> ratio. More commonly given advice is to start at 25% of RAM,
> limited to 2GB on Windows or 32-bit systems or 8GB otherwise. Try
> incremental adjustments from that point using your actual workload
> on you actual hardware to find the "sweet spot". Some DW
> environments report better performance assigning over 50% of RAM to
> shared_buffers; OLTP loads often need to reduce this to prevent
> periodic episodes of high latency.
He's asking about effective_cache_size. You seem to be talking about
shared_buffers.
Real question behind this all, is whether the e_c_s GUC is 32-bit on
32-bit systems. Because if so, it ought to be limited too. If not...
not.
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* Re: effective_cache_size on 32-bits postgres
@ 2013-03-18 18:54 Rodrigo Barboza <rodrigombufrj@gmail.com>
parent: Claudio Freire <klaussfreire@gmail.com>
0 siblings, 0 replies; 11+ messages in thread
From: Rodrigo Barboza @ 2013-03-18 18:54 UTC (permalink / raw)
To: Claudio Freire <klaussfreire@gmail.com>; +Cc: Kevin Grittner <kgrittn@ymail.com>; Pavel Stehule <pavel.stehule@gmail.com>; pgsql-performance
Yes, Claudio. You got it.
But Rob seems to have already answered the confusion between 32 and 64 bits
for effective_cache_size.
Actually I am creating generic configuration based on physical memory.
So I wanna be conservative about effective_cache_size. That's why I'm
following postgres tuning website instructions. If it says it is
conservative, that's good for me.
On Mon, Mar 18, 2013 at 3:51 PM, Claudio Freire <klaussfreire@gmail.com>wrote:
> On Mon, Mar 18, 2013 at 3:47 PM, Kevin Grittner <kgrittn@ymail.com> wrote:
> > Rodrigo Barboza <rodrigombufrj@gmail.com> wrote:
> >
> >> So setting this as half of ram, as suggested in postgres tuning
> >> webpage should be safe?
> >
> > Half of RAM is likely to be a very bad setting for any work load.
> > It will tend to result in the highest possible number of pages
> > duplicated in PostgreSQL and OS caches, reducing the cache hit
> > ratio. More commonly given advice is to start at 25% of RAM,
> > limited to 2GB on Windows or 32-bit systems or 8GB otherwise. Try
> > incremental adjustments from that point using your actual workload
> > on you actual hardware to find the "sweet spot". Some DW
> > environments report better performance assigning over 50% of RAM to
> > shared_buffers; OLTP loads often need to reduce this to prevent
> > periodic episodes of high latency.
>
>
> He's asking about effective_cache_size. You seem to be talking about
> shared_buffers.
>
> Real question behind this all, is whether the e_c_s GUC is 32-bit on
> 32-bit systems. Because if so, it ought to be limited too. If not...
> not.
>
^ permalink raw reply [nested|flat] 11+ messages in thread
end of thread, other threads:[~2013-03-18 18:54 UTC | newest]
Thread overview: 11+ messages (download: mbox mbox.gz follow: Atom feed)
-- links below jump to the message on this page --
2013-03-18 17:53 effective_cache_size on 32-bits postgres Rodrigo Barboza <rodrigombufrj@gmail.com>
2013-03-18 18:14 ` Rob Wultsch <wultsch@gmail.com>
2013-03-18 18:15 ` Pavel Stehule <pavel.stehule@gmail.com>
2013-03-18 18:18 ` Rodrigo Barboza <rodrigombufrj@gmail.com>
2013-03-18 18:18 ` Pavel Stehule <pavel.stehule@gmail.com>
2013-03-18 18:23 ` Rodrigo Barboza <rodrigombufrj@gmail.com>
2013-03-18 18:33 ` Pavel Stehule <pavel.stehule@gmail.com>
2013-03-18 18:47 ` Kevin Grittner <kgrittn@ymail.com>
2013-03-18 18:50 ` Pavel Stehule <pavel.stehule@gmail.com>
2013-03-18 18:51 ` Claudio Freire <klaussfreire@gmail.com>
2013-03-18 18:54 ` Rodrigo Barboza <rodrigombufrj@gmail.com>
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