Messages in this thread | | | Subject | Re: CFQ is worse than other IO schedulers in some cases | From | Mike Galbraith <> | Date | Wed, 18 Feb 2009 09:05:36 +0100 |
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On Wed, 2009-02-18 at 14:00 +0800, Shan Wei wrote:
> In sysbench(version:sysbench-0.4.10), I confirmed followings. > - CFQ's performance is worse than other IO schedulers when only multiple > threads test. > (There is no difference under single thread test.) > - It is worse than other IO scheduler when > I used read mode. (No regression in write mode). > - There is no difference among other IO schedulers. (e.g noop deadline) > > > The Test Result(sysbench): > UNIT:Mb/sec > __________________________________________________ > | IO | thread number | > | scheduler |-----------------------------------| > | | 1 | 3 | 5 | 7 | 9 | > +------------|------|-------|------|------|------| > |cfq | 77.8 | 32.4 | 43.3 | 55.8 | 58.5 | > |noop | 78.2 | 79.0 | 78.2 | 77.2 | 77.0 | > |anticipatory| 78.2 | 78.6 | 78.4 | 77.8 | 78.1 | > |deadline | 76.9 | 78.4 | 77.0 | 78.4 | 77.9 | > +------------------------------------------------+ My Q6600 box agrees that cfq produces less throughput doing this test, but throughput here is ~flat. Disk is external SATA ST3500820AS. _________________________________________________ | IO | thread number | | scheduler |----------------------------------| | | 1 | 3 | 5 | 7 | 9 | +------------|------|------|------|------|------| |cfq | 84.4 | 89.1 | 91.3 | 88.8 | 88.8 | |noop |102.9 | 99.3 | 99.4 | 99.7 | 98.7 | |anticipatory|100.5 |100.1 | 99.8 | 99.7 | 99.6 | |deadline | 97.9 | 98.7 | 99.5 | 99.5 | 99.3 | +-----------------------------------------------+
> Steps to reproduce(sysbench): > > (1)#echo cfq > /sys/block/sda/queue/scheduler > > (2)#sysbench --test=fileio --num-threads=1 --file-total-size=10G --file-test-mode=seqrd prepare > > (3)#sysbench --test=fileio --num-threads=1 --file-total-size=10G --file-test-mode=seqrd run > [snip] > Operations performed: 655360 Read, 0 Write, 0 Other = 655360 Total > Read 10Gb Written 0b Total transferred 10Gb (77.835Mb/sec) > 4981.44 Requests/sec executed ~~~~~~~~~~~ > (4)#sysbench --test=fileio --num-threads=1 --file-total-size=10G --file-test-mode=seqrd cleanup > > (5)#sysbench --test=fileio --num-threads=5 --file-total-size=10G --file-test-mode=seqrd prepare > (6)#sysbench --test=fileio --num-threads=5 --file-total-size=10G --file-test-mode=seqrd run > [snip] > Operations performed: 655360 Read, 0 Write, 0 Other = 655360 Total > Read 10Gb Written 0b Total transferred 10Gb (43.396Mb/sec) > 2777.35 Requests/sec executed ~~~~~~~~~~~~ > (7)#sysbench --test=fileio --num-threads=5 --file-total-size=10G --file-test-mode=seqrd cleanup > > when doing step 2 or 5, sysbench creats 128 files, and 80M each one. > when doing step 4 or 7, sysbench deletes the files. > when doing step 3 or 6, thread reads these files continuously and > reads file-block-size(default:16Kbyte) at once, just like : > > t_0 t_0 t_0 t_0 t_0 t_0 t_0 > ^ ^ ^ ^ ^ ^ ^ > ---|-----|-----|-----|-----|-----|-----|-------- > file | 16k | 16k | 16k | 16k | 16k | 16k | 16k | ... > ------------------------------------------------ > (num-threads=1) > > (t_0 stand for the first thread) > > t_0 t_1 t_2 t_3 t_4 t_0 t_1 > ^ ^ ^ ^ ^ ^ ^ > ---|-----|-----|-----|-----|-----|-----|-------- > file | 16k | 16k | 16k | 16k | 16k | 16k | 16k | ... > ------------------------------------------------ > (num-threads=5) > > (the executed threads are decide by the thread scheduler) > > > The Hardware Infos: > Arch :x86_64 > CPU :4cpu; GenuineIntel 3325.087 MHz > MEMORY :4044128kB > > ---- > Shan Wei > > -- > 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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