Date: Tue, 10 Apr 2007 16:09:44 -0400 From: Kris Kennaway <kris@obsecurity.org> To: Tom Lane <tgl@sss.pgh.pa.us> Cc: pgsql-hackers <pgsql-hackers@postgresql.org>, performance@FreeBSD.org, current@FreeBSD.org, Mark Kirkwood <markir@paradise.net.nz>, Kris Kennaway <kris@obsecurity.org> Subject: Re: [HACKERS] Anyone interested in improving postgresql scaling? Message-ID: <20070410200944.GA73534@xor.obsecurity.org> In-Reply-To: <555.1176234720@sss.pgh.pa.us> References: <20070226002234.GA80974@xor.obsecurity.org> <461B69C0.4060707@paradise.net.nz> <25573.1176215022@sss.pgh.pa.us> <20070410184332.GC44123@xor.obsecurity.org> <28537.1176230816@sss.pgh.pa.us> <20070410194508.GA73072@xor.obsecurity.org> <555.1176234720@sss.pgh.pa.us>
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--HlL+5n6rz5pIUxbD Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Apr 10, 2007 at 03:52:00PM -0400, Tom Lane wrote: > Kris Kennaway <kris@obsecurity.org> writes: > > On Tue, Apr 10, 2007 at 02:46:56PM -0400, Tom Lane wrote: > >> Oh, I'm sure the BSD kernel acts as you describe. But Mark's point is > >> that Postgres never has more than one process waiting on any particular > >> SysV semaphore, and so the problem doesn't really affect us. >=20 > > To be clear, some behaviour that postgresql does with sysv semaphores > > causes wakeups of many processes at once. i.e. if you have 20 > > clients, you will get up to 20 wakeups. I haven't studied the precise > > cause of this, but it is empirically true. This is the scaling > > problem I described, and it's what mux's patch addresses. >=20 > [ shrug... ] To the extent that that happens, it's Postgres' own issue, > and no amount of kernel rejiggering will change it. But I certainly > have no objection to a patch that fixes the kernel behavior ... As we've discussed before, by far the bigger issue with postgresql performance on FreeBSD is the default setting of update_process_titles=3Don. Kris --HlL+5n6rz5pIUxbD Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (FreeBSD) iD8DBQFGG+8HWry0BWjoQKURAkleAKDmbOCNbFOMGymoOWUAahlAectF9wCdEiRV QF1Y1ncUaTBcw2+UCNoRYfM= =ZPuL -----END PGP SIGNATURE----- --HlL+5n6rz5pIUxbD--
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