Messages in this thread | | | Date | Mon, 12 Sep 2011 17:09:20 +0400 | Subject | Re: [PATCH 1/1] CFQ: fix handling 'deep' cfqq | From | Maxim Patlasov <> |
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Shaohua,
>> So the key problem here is how to detect if a device is fast. Doing >> the detection >> in the dispatch stage always can't give us correct result. A fast device really >> should be requests can be finished in short time. So I have something attached. >> In my environment, a hard disk is detected slow and a ssd is detected fast, but >> I haven't run any benchmark so far. How do you think about it? > > Thanks for the patch, I'll test it in several h/w configurations soon > and let you know about results.
1. Single slow disk (ST3200826AS). Eight instances of aio-stress, cmd-line:
# aio-stress -a 4 -b 4 -c 1 -r 4 -O -o 0 -t 1 -d 1 -i 1 -s 16 f1_$I f2_$I f3_$I f4_$I
Aggreagate throughput:
Pristine 3.1.0-rc5 (CFQ): 3.77 MB/s Pristine 3.1.0-rc5 (noop): 2.63 MB/s Pristine 3.1.0-rc5 (CFQ, slice_idle=0): 2.81 MB/s 3.1.0-rc5 + my patch (CFQ): 5.76 MB/s 3.1.0-rc5 + your patch (CFQ): 5.61 MB/s
2. Four modern disks (WD1003FBYX) assembled in RAID-0 (Adaptec AAC-RAID (rev 09) 256Mb RAM). Eight instances of aio-stress with think-time 1msec:
> --- aio-stress-orig.c 2011-08-16 17:00:04.000000000 -0400 > +++ aio-stress.c 2011-08-18 14:49:31.000000000 -0400 > @@ -884,6 +884,7 @@ static int run_active_list(struct thread > } > if (num_built) { > ret = run_built(t, num_built, t->iocbs); > + usleep(1000); > if (ret < 0) { > fprintf(stderr, "error %d on run_built\n", ret); > exit(1);
Cmd-line:
# aio-stress -a 4 -b 4 -c 1 -r 4 -O -o 0 -t 1 -d 1 -i 1 f1_$I f2_$I f3_$I f4_$I
Aggreagate throughput:
Pristine 3.1.0-rc5 (CFQ): 63.67 MB/s Pristine 3.1.0-rc5 (noop): 100.8 MB/s Pristine 3.1.0-rc5 (CFQ, slice_idle=0): 105.63 MB/s 3.1.0-rc5 + my patch (CFQ): 105.59 MB/s 3.1.0-rc5 + your patch (CFQ): 14.36 MB/s
So, to meet needs of striped raids, it's not enough to measure service time of separate requests. We need somehow to measure whether given hdd/raid is able to service many requests simultaneously in an effective way.
Thanks, Maxim
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