Date: Wed, 18 Jul 2007 13:48:16 -0500
From: "Jim C. Nasby" <decibel@decibel.org>
To: Heikki Linnakangas <heikki@enterprisedb.com>
Cc: Ron Mayer <rm_pg@cheapcomplexdevices.com>,
 pgsql-performance@postgresql.org
Subject: Re: ionice to make vacuum friendier?
Message-ID: <20070718184816.GB39272@nasby.net>
References: <f7jfs1$ntm$1@news.hub.org> <469DD744.1060906@enterprisedb.com>
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On Wed, Jul 18, 2007 at 10:03:00AM +0100, Heikki Linnakangas wrote:
> Ron Mayer wrote:
> > Seems Linux has IO scheduling through a program called ionice.
> >=20
> > Has anyone here experimented with using it rather than
> > vacuum sleep settings?
>=20
> I looked at that briefly for smoothing checkpoints, but it was
> unsuitable for that purpose because it only prioritizes reads, not writes.
>=20
> It maybe worth trying for vacuum, though vacuum too can do a lot of
> writes. In the worst case, the OS cache is saturated with dirty pages,
> which blocks all writes in the system.
>=20
> If it did prioritize writes as well, that would be *excellent*. Any
> kernel hackers out there looking for a project?

My understanding is that FreeBSD will prioritize IO based on process
priority, though I have no idea how it's actually accomplished or how
effective it is. But if we put in special support for this for Linux we
should consider FBSD as well.
--=20
Jim Nasby                                      decibel@decibel.org
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)

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