Messages in this thread | | | Date | Fri, 1 May 2015 09:20:58 +0800 | Subject | Re: [PATCH] block: loop: avoiding too many pending per work I/O | From | Ming Lei <> |
| |
On Fri, May 1, 2015 at 12:59 AM, Jeff Moyer <jmoyer@redhat.com> wrote: > Ming Lei <ming.lei@canonical.com> writes: > >> On Wed, Apr 29, 2015 at 12:36 AM, Jeff Moyer <jmoyer@redhat.com> wrote: >>> Ming Lei <ming.lei@canonical.com> writes: >>> >>>> If there are too many pending per work I/O, too many >>>> high priority work thread can be generated so that >>>> system performance can be effected. >>>> >>>> This patch limits the max pending per work I/O as 16, >>>> and will fackback to single queue mode when the max >>>> number is reached. >>> >>> Actually, it limits it to 32. Also, there is no discussion on what >>> variables might affect this number. Will that magic number change >>> depending on the number of cpus on the system, for example? >> >> My fault, it should have been 16. >> >> It is just used to keep more IOs in flight, but can't cause obvious >> costs like the case of Fedora live booting. >> >> IMO, it shouldn't depend much on number of CPUs, and more >> related with I/O performance of the backing file, and the number >> is like 'iodepth' of fio. > > OK, that makes more sense. I'm still not a huge fan of hard-coding > numbers that are storage-specific, but I don't have a better suggestion > at the moment, either.
OK, thanks for your review.
| |