From: Andres Freund <andres@2ndquadrant.com>
To: Metin Doslu <metin@citusdata.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Cc: Amit Kapila <amit.kapila16@gmail.com>
Cc: Claudio Freire <klaussfreire@gmail.com>
Subject: Re: Parallel Select query performance and shared buffers
Date: Thu, 5 Dec 2013 10:18:41 +0100
Message-ID: <20131205091841.GE28793@alap2.anarazel.de> (raw)
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On 2013-12-05 11:15:20 +0200, Metin Doslu wrote:
> > - When we increased NUM_BUFFER_PARTITIONS to 1024, this problem is
> > disappeared for 8 core machines and come back with 16 core machines on
> > Amazon EC2. Would it be related with PostgreSQL locking mechanism?
>
> If we build with -DLWLOCK_STATS to print locking stats from PostgreSQL, we
> see tons of contention with default value of NUM_BUFFER_PARTITIONS which is
> 16:
Is your workload bigger than RAM? I think a good bit of the contention
you're seeing in that listing is populating shared_buffers - and might
actually vanish once you're halfway cached.
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To: pgsql-performance@postgresql.org
Cc: andres@2ndquadrant.com, metin@citusdata.com, pgsql-hackers@postgresql.org, amit.kapila16@gmail.com, klaussfreire@gmail.com
Subject: Re: Parallel Select query performance and shared buffers
In-Reply-To: <20131205091841.GE28793@alap2.anarazel.de>
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