Seems Linux has IO scheduling through a program called ionice.

Has anyone here experimented with using it rather than
vacuum sleep settings?

http://linux.die.net/man/1/ionice
This program sets the io scheduling class and priority
for a program. As of this writing, Linux supports 3 scheduling
classes:

Idle. A program running with idle io priority will only get disk
time when no other program has asked for disk io for a defined
grace period. The impact of idle io processes on normal system
activity should be zero.[...]

Best effort. This is the default scheduling class for any process
that hasn't asked for a specific io priority. Programs inherit the
CPU nice setting for io priorities. [...]

http://friedcpu.wordpress.com/2007/0...ng-ionice-yet/

Ron Mayer wrote:
> Seems Linux has IO scheduling through a program called ionice.
>
> Has anyone here experimented with using it rather than
> vacuum sleep settings?

I looked at that briefly for smoothing checkpoints, but it was
unsuitable for that purpose because it only prioritizes reads, not writes.

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.

If it did prioritize writes as well, that would be *excellent*. Any
kernel hackers out there looking for a project?

--
Heikki Linnakangas
EnterpriseDB http://www.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.
> >
> > Has anyone here experimented with using it rather than
> > vacuum sleep settings?
>
> I looked at that briefly for smoothing checkpoints, but it was
> unsuitable for that purpose because it only prioritizes reads, not writes.
>
> 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.
>
> 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.
--
Jim Nasby decibel@decibel.org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)

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