Messages in this thread |  | | | Date | Sun, 11 May 2008 14:14:06 +0100 | | From | "Daniel J Blueman" <> | | Subject | Re: performance "regression" in cfq compared to anticipatory, deadline and noop |
I've been experiencing this for a while also; an almost 50% regression
is seen for single-process reads (ie sync) if slice_idle is 1ms or
more (eg default of 8) [1], which seems phenomenal.
Jens, is this the expected price to pay for optimal busy-spindle
scheduling, a design issue, bug or am I missing something totally?
Thanks,
Daniel
--- [1]
# cat /sys/block/sda/queue/iosched/slice_idle
8
# echo 1 >/proc/sys/vm/drop_caches
# dd if=/dev/sda of=/dev/null bs=64k count=5000
5000+0 records in
5000+0 records out
327680000 bytes (328 MB) copied, 4.92922 s, 66.5 MB/s
# echo 0 >/sys/block/sda/queue/iosched/slice_idle
# echo 1 >/proc/sys/vm/drop_caches
# dd if=/dev/sda of=/dev/null bs=64k count=5000
5000+0 records in
5000+0 records out
327680000 bytes (328 MB) copied, 2.74098 s, 120 MB/s
# hdparm -Tt /dev/sda
/dev/sda:
Timing cached reads: 15464 MB in 2.00 seconds = 7741.05 MB/sec
Timing buffered disk reads: 342 MB in 3.01 seconds = 113.70 MB/sec
[120MB/s is known platter-rate for this disc, so expected]
--
Daniel J Blueman
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