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Date:      Tue, 6 Nov 2012 18:51:37 -0700
From:      "Samuel J. Greear" <sjg@evilcode.net>
To:        Yuri <yuri@rawbw.com>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: pgbench performance is lagging compared to Linux and DragonflyBSD?
Message-ID:  <CANY-Wm9iHS92_CzDJUCs1COC7-v0xt%2BT%2BCqrMq%2BPkshZ04UPtQ@mail.gmail.com>
In-Reply-To: <50997AB8.40607@rawbw.com>
References:  <50980ADD.4010402@rawbw.com> <CAGH67wScvnE7gYzVVtfehYbVfM465vrLjP9bX4KXSp8Sq-25mA@mail.gmail.com> <50994FE0.2070205@rawbw.com> <CANY-Wm9nTPy5A3Eygb4BQmz60a8ose--3veoQHwFj3p66BFB8Q@mail.gmail.com> <50997AB8.40607@rawbw.com>

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On Tue, Nov 6, 2012 at 2:01 PM, Yuri <yuri@rawbw.com> wrote:
> On 11/06/2012 11:10, Samuel J. Greear wrote:
>>
>> Single and multi-socket hardware are not really directly comparable in
>> PostgreSQL tests.
>
>
> So if the CPUs are split between sockets, would such system generally
> perform better or worse with PostgeSQL vs. non-split situation?
>
> Yuri

Unless the algorithms you are testing are able to operate entirely out
of the processors caches (and PostgreSQL does not fall into that
category) performance will be generally lower as you add sockets.
FreeBSD's ULE scheduler is aware of this and takes it into account,
but the performance ULE is able to maintain across sockets (this
applies to other OS's schedulers too) is more damage control than
anything else.

Sam



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