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References: <4E92F294.9010405@gmail.com> <4E92FB87.1030703@peak6.com>
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Date: Mon, 10 Oct 2011 16:14:35 +0100 (BST)
From: Leonardo Francalanci <m_lists@yahoo.it>
Reply-To: Leonardo Francalanci <m_lists@yahoo.it>
Subject: Re: Adding more memory = hugh cpu load
To: "sthomas@peak6.com" <sthomas@peak6.com>,
	alexandre - aldeia digital <adaldeia@gmail.com>
Cc: "pgsql-performance@postgresql.org" <pgsql-performance@postgresql.org>
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=0A=0A> That's not entirely surprising. The problem with having lots of mem=
ory is... =0A> that you have lots of memory. The operating system likes to =
cache, and this =0A> includes writes. Normally this isn't a problem, but wi=
th 48GB of RAM, the =0A> defaults (for CentOS 5.5 in particular) are to use=
 up to 40% of that to cache =0A> writes.=0A=0A=0AI don't understand: don't =
you want postgresql to issue the fsync calls when=0Ait "makes sense" (and c=
onfigure them), rather than having the OS decide=0Awhen it's best to flush =
to disk? That is: don't you want all the memory to=0Abe used for caching, u=
nless postgresql says otherwise (calling fsync), instead=0Aof "as soon as 1=
% of memory is used"?=0A