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Date:      Thu, 23 Feb 2012 08:22:16 -0500
From:      John Baldwin <jhb@freebsd.org>
To:        freebsd-hackers@freebsd.org
Cc:        "hackers@freebsd.org" <hackers@freebsd.org>, Doug Barton <dougb@freebsd.org>, Ivan Voras <ivoras@freebsd.org>
Subject:   Re: PostgreSQL benchmarks (now with Linux numbers)
Message-ID:  <201202230822.16304.jhb@freebsd.org>
In-Reply-To: <4F45AB76.5050201@FreeBSD.org>
References:  <b1732c99-eec2-4097-ad9c-f58979addf9f@email.android.com> <4F45AB76.5050201@FreeBSD.org>

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On Wednesday, February 22, 2012 9:59:02 pm Doug Barton wrote:
> On 02/22/2012 01:42, Ivan Voras wrote:
> > The Dragonfly team has recently liberated their VM from the giant lock and there are some interesting benchmarks comparing it to FreeBSD 9 and a 
derivative of RedHat Enterprise Linux:
> > 
> > http://leaf.dragonflybsd.org/mailarchive/kernel/2011-11/msg00008.html
> > 
> > Other developments are described in their release notes: http://www.dragonflybsd.org/release30/
> 
> The 4.5 times improvement by enabling kern.ipc.shm_use_phys is pretty
> notable, what prevents us from enabling that by default?

It makes all your SYSV SHMs wired.  That's fine if you are running a dedicated
server using SYSV SHMs where you want that process to use all the RAM in the
machine (e.g. a pgqsl server).  It's not so great for a general purpose load
where you would like an otherwise-idle process using SYSV SHMs to have the SHMs
paged out to swap if other processes on the machine need memory and the box is
under memory pressure.

-- 
John Baldwin



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