Re: ionice to make vacuum friendier?

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(at)decibel(dot)org
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)