Messages in this thread | | | Date | Thu, 26 Mar 2009 07:38:51 -0700 | From | Andrew Morton <> | Subject | Re: ext3 IO latency measurements (was: Linux 2.6.29) |
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On Thu, 26 Mar 2009 10:06:30 +0100 Ingo Molnar <mingo@elte.hu> wrote:
> And it's not just sys_fsync(). The script i wrote tests file read > latencies. I have created 1000 files with the same size (all copies > of kernel/sched.c ;-), and tested their cache-cold plain-cat > performance via: > > for ((i=0;i<1000;i++)); do > printf "file #%4d, plain reading it took: " $i > /usr/bin/time -f "%e seconds." cat $i >/dev/null > done > > I.e. plain, supposedly high-prio reads. The result is very common > hickups in read latencies: > > file # 579 (253560 bytes), reading it took: 0.08 seconds. > file # 580 (253560 bytes), reading it took: 0.05 seconds. > file # 581 (253560 bytes), reading it took: 0.01 seconds. > file # 582 (253560 bytes), reading it took: 0.01 seconds. > file # 583 (253560 bytes), reading it took: 4.61 seconds. > file # 584 (253560 bytes), reading it took: 1.29 seconds. > file # 585 (253560 bytes), reading it took: 3.01 seconds. > file # 586 (253560 bytes), reading it took: 7.74 seconds. > file # 587 (253560 bytes), reading it took: 3.22 seconds. > file # 588 (253560 bytes), reading it took: 0.05 seconds. > file # 589 (253560 bytes), reading it took: 0.36 seconds. > file # 590 (253560 bytes), reading it took: 7.39 seconds. > file # 591 (253560 bytes), reading it took: 7.58 seconds. > file # 592 (253560 bytes), reading it took: 7.90 seconds. > file # 593 (253560 bytes), reading it took: 8.78 seconds. > file # 594 (253560 bytes), reading it took: 8.01 seconds. > file # 595 (253560 bytes), reading it took: 7.47 seconds. > file # 596 (253560 bytes), reading it took: 11.52 seconds. > file # 597 (253560 bytes), reading it took: 10.33 seconds. > file # 598 (253560 bytes), reading it took: 8.56 seconds. > file # 599 (253560 bytes), reading it took: 7.58 seconds.
(gets deja-vu feelings)
http://lkml.org/lkml/2003/2/21/10
Maybe you should be running a 2.5.61 kernel.
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