Thread: ionice to make vacuum friendier?
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/2007/07/17/why-arent-you-using-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
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)