On Fri, May 1, 2015 at 12:59 AM, Jeff Moyer <[email protected]> wrote: > Ming Lei <[email protected]> writes: > >> On Wed, Apr 29, 2015 at 12:36 AM, Jeff Moyer <[email protected]> wrote: >>> Ming Lei <[email protected]> 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.
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