http://bugzilla.kernel.org/show_bug.cgi?id=14208
--- Comment #6 from Török Edwin <edwintorok@xxxxxxxxx> 2009-09-22 19:08:43 ---
Well with the truncat case xfs spends a lot of time writing files, at only
~8-10Mb/s, while my disk can do a 160-200Mb/s on same partition with a dd.
Is it that its flushing lots of small files the problem?
Maybe the I/O scheduler could be taught to recognize writes to the same
location
and ignore the initial writes.
iostat -k 5 with dd if=/dev/zero of=/var/tmp/foo bs=1M count=1000
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 165.20 0.00 64010.40 0 320052
sdb 166.00 0.00 64112.80 0 320564
sdc 164.20 0.00 64197.60 0 320988
sdd 141.00 0.00 62476.00 0 312380
sde 164.60 0.00 64386.40 0 321932
sdf 162.20 0.00 64300.00 0 321500
sdg 0.00 0.00 0.00 0 0
md3 0.00 0.00 0.00 0 0
md4 5337.60 0.00 204596.80 0 1022984
dm-0 0.00 0.00 0.00 0 0
dm-1 5334.20 0.00 204583.20 0 1022916
dm-2 3.40 0.00 13.60 0 68
dm-3 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
1.06 0.00 7.65 37.87 0.00 53.42
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 149.80 2.40 58213.60 12 291068
sdb 149.60 0.00 58213.60 0 291068
sdc 145.60 0.00 58111.20 0 290556
sdd 145.60 0.80 66371.20 4 331856
sde 145.80 0.00 58177.60 0 290888
sdf 145.20 0.00 57996.00 0 289980
sdg 0.00 0.00 0.00 0 0
md3 0.40 1.60 0.00 8 0
md4 3681.40 1.60 159506.40 8 797532
dm-0 0.20 1.60 0.00 8 0
dm-1 3678.80 0.00 159496.80 0 797484
dm-2 2.40 0.00 9.60 0 48
dm-3 0.00 0.00 0.00 0 0
iostat -k 5 with the seq loop echoing something to same file:
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 1.60 0.00 15.20 0 76
sdb 1.80 0.80 15.20 4 76
sdc 135.40 0.00 549.60 0 2748
sdd 1.40 0.00 20.00 0 100
sde 1.40 0.00 20.00 0 100
sdf 135.60 0.00 550.40 0 2752
sdg 133.80 0.00 8563.20 0 42816
md3 0.00 0.00 0.00 0 0
md4 146.40 0.00 585.60 0 2928
dm-0 0.00 0.00 0.00 0 0
dm-1 133.80 0.00 535.20 0 2676
dm-2 12.60 0.00 50.40 0 252
dm-3 0.00 0.00 0.00 0 0
avg-cpu: %user %nice %system %iowait %steal %idle
4.66 0.00 4.71 0.34 0.00 90.28
Device: tps kB_read/s kB_wrtn/s kB_read kB_wrtn
sda 0.20 0.00 0.10 0 0
sdb 0.20 0.00 0.10 0 0
sdc 131.80 0.00 535.20 0 2676
sdd 0.80 0.00 4.80 0 24
sde 1.00 0.80 4.80 4 24
sdf 132.00 0.00 536.00 0 2680
sdg 131.20 0.00 8396.80 0 41984
md3 0.00 0.00 0.00 0 0
md4 135.20 0.80 540.10 4 2700
dm-0 0.00 0.00 0.00 0 0
dm-1 132.20 0.80 528.10 4 2640
dm-2 3.00 0.00 12.00 0 60
dm-3 0.00 0.00 0.00 0 0
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