Date: Thu, 23 Feb 2012 14:46:04 +0000 From: Vlad Galu <dudu@dudu.ro> To: Damien Fleuriot <ml@my.gd> Cc: freebsd-hackers@freebsd.org Subject: Re: PostgreSQL benchmarks (now with Linux numbers) Message-ID: <CA%2BFTnKOBSh_gzQdtHxsyE2sZEM%2B9TbPgz=%2BsK_iCzM9FqEizJQ@mail.gmail.com> In-Reply-To: <4F46500D.3070609@my.gd> References: <b1732c99-eec2-4097-ad9c-f58979addf9f@email.android.com> <4F45AB76.5050201@FreeBSD.org> <201202230822.16304.jhb@freebsd.org> <4F46500D.3070609@my.gd>
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On Thu, Feb 23, 2012 at 2:41 PM, Damien Fleuriot <ml@my.gd> wrote: > > > On 2/23/12 2:22 PM, John Baldwin wrote: > > 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, any chance we can get that in layman's terms ? > > I'm totally no coder, but I'd really like if we could do this at my work > place to increase our firewalls' performances. > Hi Damien, The above setting prevents the SYSV shared memory from being swapped by the pager. It is useful in a database context, where you want the pages to be available imediately, without having to wait until they are loaded back from disk (in a memory constrained environment). I won't help your firewall at all. -- Good, fast & cheap. Pick any two.
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