Messages in this thread | | | Date | Wed, 8 Apr 2009 21:56:10 +0200 | From | Heinz Diehl <> | Subject | Re: SSD and IO schedulers |
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On 08.04.2009, Corrado Zoccolo wrote:
> I found that elevator=deadline performs much better than noop for > writes, and almost as well for reads [....]
The DL elevator has slightly more throughput than cfq and anticipatory, but is almost unusuable under load.
Running Theodore Ts'os "fsync-tester" while doing Linus' torture test "while : ; do time sh -c "dd if=/dev/zero of=bigfile bs=8M count=256 ; sync; rm bigfile"; done" shows it clearly:
mount: /dev/sda4 on /home type xfs (rw,noatime,logbsize=256k,logbufs=2,nobarrier) Kernel 2.6.29.1 (vanilla)
with cfq:
htd@liesel:~/!> ./fsync-tester fsync time: 0.7640 fsync time: 0.6166 fsync time: 1.2830 fsync time: 0.4273 fsync time: 1.1693 fsync time: 1.7466 fsync time: 1.2477 fsync time: 1.9411 fsync time: 1.9636 fsync time: 1.9065 fsync time: 1.1561 fsync time: 1.8267 fsync time: 0.2431 fsync time: 0.2898 fsync time: 0.2394 fsync time: 0.4309 fsync time: 1.5699 fsync time: 0.3742 fsync time: 1.3194 fsync time: 1.9442 fsync time: 1.0899 fsync time: 1.9443 fsync time: 1.0062
with dl:
fsync time: 10.5853 fsync time: 10.3339 fsync time: 5.3374 fsync time: 6.5707 fsync time: 10.6095 fsync time: 4.1154 fsync time: 4.9604 fsync time: 10.5325 fsync time: 10.4543 fsync time: 10.4970 fsync time: 10.5570 fsync time: 5.2717 fsync time: 10.5619 fsync time: 5.3058 fsync time: 3.1019 fsync time: 5.1504 fsync time: 5.7564 fsync time: 10.5998 fsync time: 4.0895
Regards, Heinz.
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