From: SASIKUMAR Devaraj <sashikumard@yahoo.com>
To: Campbell, Lance <lance@illinois.edu>
To: Bruce Momjian <bruce@momjian.us>
Cc: Laurenz Albe <laurenz.albe@cybertec.at>
Cc: MichaelDBA <michaeldba@sqlexec.com>
Cc: holger@jakobs.com <holger@jakobs.com>
Cc: pgsql-admin@lists.postgresql.org <pgsql-admin@lists.postgresql.org>
Subject: Re: work_mem
Date: Sat, 3 Apr 2021 05:23:56 +0000 (UTC)
Message-ID: <230367927.2421710.1617427436762@mail.yahoo.com> (raw)
In-Reply-To: <20210402153436.GE9270@momjian.us>
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<c1e02a03-71cd-4071-e000-967403bcab9d@sqlexec.com>
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<592e5895-8dbd-1a4f-a87c-af72ac8eea02@sqlexec.com>
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<339e1ee870881a3efaffc7ea4cddac6bc4d009cf.camel@cybertec.at>
<20210402150736.GD9270@momjian.us>
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<20210402153436.GE9270@momjian.us>
Hi All
One basic doubt.
Whether work_mem is allocated for each clients connected to Database or for against the Sort Operations(Queries) in database? Please clarify
Case 1: work_mem=4mTotal Sessions connected=100Total=400M
Or Case 2work_mem=4mTotal Sort operations at DB now=50Total work_mem=200M
Please clarify at high level whether Case 1 is true or Case 2 is true?
Regards
Sasi On Friday, 2 April, 2021, 09:04:56 pm IST, Bruce Momjian <bruce@momjian.us> wrote:
On Fri, Apr 2, 2021 at 03:25:04PM +0000, Campbell, Lance wrote:
> Thanks for sharing this thread. My suggestion of having a work_mem_stack_size
> is the same concept mentioned in this thread regarding having a work_mem_pool.
> I prefer this later term rather than the one I was using. When the work mem
> pool is exhausted PostgreSQL just uses temp files for work_mem. With current
> statics for temp files and with a new stats on a work mem pool usage a user
> could fine tune memory much more precisely. It would leave the “art of memory
> tuning” behind. The other added benefit is that people would have a better
> understanding of how work_mem is used by naturally having to explain what a
> work_mem_pool is and when it is drawn on. There are probably a lot of
> PostgreSQL instance that would run faster just by having the confidence to
> increase the size of work_mem. I am sure many instances have this value set to
> low.
Uh, did you read the blog before it, referenced in that blog entry:
https://momjian.us/main/blogs/pgblog/2018.html#December_7_2018
Even if we have a pool, it is still complex to configure memory, but it
might help.
--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com
If only the physical world exists, free will is an illusion.
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Subject: Re: work_mem
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