Messages in this thread | | | Date | Fri, 14 Jan 2011 12:44:09 +0800 | Subject | Re: [PATCH 1/2]block cfq: make queue preempt work for queues from different workload | From | Shaohua Li <> |
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2011/1/12 Shaohua Li <shaohua.li@intel.com>: > Hi, > On Wed, Jan 12, 2011 at 05:07:47AM +0800, Corrado Zoccolo wrote: >> Hi Shaohua, >> On Tue, Jan 11, 2011 at 9:51 AM, Shaohua Li <shaohua.li@intel.com> wrote: >> > I got this: >> > fio-874 [007] 2157.724514: 8,32 m N cfq874 preempt >> > fio-874 [007] 2157.724519: 8,32 m N cfq830 slice expired t=1 >> > fio-874 [007] 2157.724520: 8,32 m N cfq830 sl_used=1 disp=0 charge=1 iops=0 sect=0 >> > fio-874 [007] 2157.724521: 8,32 m N cfq830 set_active wl_prio:0 wl_type:0 >> > fio-874 [007] 2157.724522: 8,32 m N cfq830 Not idling. st->count:1 >> > cfq830 is an async queue, and preempted by a sync queue cfq874. But since we >> > have cfqg->saved_workload_slice mechanism, the preempt is a nop. >> > Looks currently our preempt is totally broken if the two queues are not from >> > the same workload type. >> > Below patch fixes it. This will might make async queue starvation, but it's >> > what our old code does before cgroup is added. >> have you measured latency improvements by un-breaking preemption? >> AFAIK, preemption behaviour changed since 2.6.33, before cgroups were >> added, and the latency before the changes that weakened preemption in >> 2.6.33 was far worse. > Yes. I'm testing a SD card for MeeGo. The random write is very slow (~12k/s) but > random read is relatively fast > 1M/s. > > Without patch: > write: (groupid=0, jobs=1): err= 0: pid=3876 > write: io=966656 B, bw=8054 B/s, iops=1 , runt=120008msec > clat (usec): min=5 , max=1716.3K, avg=88637.38, stdev=207100.44 > lat (usec): min=5 , max=1716.3K, avg=88637.69, stdev=207100.41 > bw (KB/s) : min= 0, max= 52, per=168.17%, avg=11.77, stdev= 8.85 > read: (groupid=0, jobs=1): err= 0: pid=3877 > read : io=52516KB, bw=448084 B/s, iops=109 , runt=120014msec > slat (usec): min=7 , max=1918.5K, avg=519.78, stdev=25777.85 > clat (msec): min=1 , max=2728 , avg=71.17, stdev=216.92 > lat (msec): min=1 , max=2756 , avg=71.69, stdev=219.52 > bw (KB/s) : min= 1, max= 1413, per=66.42%, avg=567.22, stdev=461.50 > > With patch: > write: (groupid=0, jobs=1): err= 0: pid=4884 > write: io=81920 B, bw=677 B/s, iops=0 , runt=120983msec > clat (usec): min=13 , max=742976 , avg=155694.10, stdev=244610.02 > lat (usec): min=13 , max=742976 , avg=155694.50, stdev=244609.89 > bw (KB/s) : min= 0, max= 31, per=inf%, avg= 8.40, stdev=12.78 > read: (groupid=0, jobs=1): err= 0: pid=4885 > read : io=133008KB, bw=1108.3KB/s, iops=277 , runt=120022msec > slat (usec): min=8 , max=1159.1K, avg=164.24, stdev=9116.65 > clat (msec): min=1 , max=1988 , avg=28.34, stdev=55.81 > lat (msec): min=1 , max=1989 , avg=28.51, stdev=57.51 > bw (KB/s) : min= 2, max= 1808, per=51.10%, avg=1133.42, stdev=275.59 > > Both read latency/throughput has big difference with the patch, but write > gets starvation. Hi Jens and others, How do you think about the patch?
Thanks, Shaohua -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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