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Date: Fri, 1 May 2015 09:20:58 +0800 From: Ming Lei <ming.lei@...onical.com> To: Jeff Moyer <jmoyer@...hat.com> Cc: Jens Axboe <axboe@...nel.dk>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "Justin M. Forbes" <jforbes@...oraproject.org>, "v4.0" <stable@...r.kernel.org> Subject: Re: [PATCH] block: loop: avoiding too many pending per work I/O On Fri, May 1, 2015 at 12:59 AM, Jeff Moyer <jmoyer@...hat.com> wrote: > Ming Lei <ming.lei@...onical.com> writes: > >> On Wed, Apr 29, 2015 at 12:36 AM, Jeff Moyer <jmoyer@...hat.com> wrote: >>> Ming Lei <ming.lei@...onical.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. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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