Hi
I am running a very simple randrw workload
if I uncomment the thinktime line, the latencies reported become much
larger.
It doesn't make senes to me that a lower disk load results in higher
latencies.
can anyone please tell me if I am wrongly interpreting the output ?
thanks!!
[global]
size=256m
directory=/mnt/vda2/tmp
invalidate=1
runtime=90
clat_percentiles=0
#thinktime=10000
[bgupdater]
rw=randrw
ioengine=libaio
direct=1
iodepth=16
without thinktime (high KB/s) - latency about 11ms (it's an ssd drive)
bgupdater: (g=0): rw=randrw, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio,
iodepth=16
fio-2.1
Starting 1 process
Jobs: 1 (f=1): [m] [100.0% done] [2788KB/2836KB/0KB /s] [697/709/0 iops]
[eta 00m:00s]
bgupdater: (groupid=0, jobs=1): err= 0: pid=2827: Fri May 17 00:40:18 2013
read : io=131220KB, bw=2718.5KB/s, iops=679, runt= 48270msec
slat (usec): min=3, max=22626, avg=25.35, stdev=196.44
clat (usec): min=68, max=42871, avg=11013.43, stdev=5577.65
lat (usec): min=337, max=42898, avg=11039.70, stdev=5577.81
bw (KB /s): min= 2051, max= 3320, per=99.85%, avg=2713.95,
stdev=273.34
write: io=130924KB, bw=2712.4KB/s, iops=678, runt= 48270msec
slat (usec): min=5, max=22547, avg=27.85, stdev=169.45
clat (usec): min=792, max=40276, avg=12491.74, stdev=6069.90
lat (usec): min=806, max=47342, avg=12520.54, stdev=6072.64
bw (KB /s): min= 2096, max= 3209, per=99.96%, avg=2710.88,
stdev=210.73
lat (usec) : 100=0.01%, 250=0.01%, 500=0.38%, 750=1.75%, 1000=0.50%
lat (msec) : 2=1.03%, 4=1.02%, 10=46.23%, 20=39.03%, 50=10.06%
cpu : usr=1.50%, sys=5.51%, ctx=51567, majf=0, minf=24
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=100.0%, 32=0.0%,
>=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%,
>=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.1%, 32=0.0%, 64=0.0%,
>=64=0.0%
issued : total=r=32805/w=32731/d=0, short=r=0/w=0/d=0
Run status group 0 (all jobs):
READ: io=131220KB, aggrb=2718KB/s, minb=2718KB/s, maxb=2718KB/s,
mint=48270msec, maxt=48270msec
WRITE: io=130924KB, aggrb=2712KB/s, minb=2712KB/s, maxb=2712KB/s,
mint=48270msec, maxt=48270msec
Disk stats (read/write):
vda: ios=32721/32686, merge=0/30, ticks=359611/407708, in_queue=767361,
util=99.87%
re-runing after having introduced thinktime=10000
much lower bandwitdh, but 152ms latency !
bgupdater: (g=0): rw=randrw, bs=4K-4K/4K-4K/4K-4K, ioengine=libaio,
iodepth=16
fio-2.1
Starting 1 process
Jobs: 1 (f=1): [m] [100.0% done] [200KB/192KB/0KB /s] [50/48/0 iops] [eta
00m:00s]
bgupdater: (groupid=0, jobs=1): err= 0: pid=2833: Fri May 17 00:43:21 2013
read : io=17768KB, bw=202135B/s, iops=49, runt= 90011msec
slat (usec): min=6, max=166, avg=29.62, stdev=15.64
clat (usec): min=632, max=157715, avg=152132.61, stdev=5965.84
lat (usec): min=797, max=157744, avg=152163.37, stdev=5965.66
bw (KB /s): min= 102, max= 276, per=99.84%, avg=196.68, stdev=27.96
write: io=17720KB, bw=201589B/s, iops=49, runt= 90011msec
slat (usec): min=8, max=164, avg=34.02, stdev=16.60
clat (msec): min=20, max=157, avg=152.23, stdev= 4.09
lat (msec): min=20, max=157, avg=152.27, stdev= 4.09
bw (KB /s): min= 118, max= 291, per=100.00%, avg=196.23,
stdev=27.95
lat (usec) : 750=0.01%
lat (msec) : 20=0.02%, 50=0.07%, 100=0.11%, 250=99.79%
cpu : usr=0.12%, sys=0.36%, ctx=8891, majf=0, minf=24
IO depths : 1=0.1%, 2=0.1%, 4=0.1%, 8=0.1%, 16=99.8%, 32=0.0%,
>=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%,
>=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.1%, 32=0.0%, 64=0.0%,
>=64=0.0%
issued : total=r=4442/w=4430/d=0, short=r=0/w=0/d=0
Run status group 0 (all jobs):
READ: io=17768KB, aggrb=197KB/s, minb=197KB/s, maxb=197KB/s,
mint=90011msec, maxt=90011msec
WRITE: io=17720KB, aggrb=196KB/s, minb=196KB/s, maxb=196KB/s,
mint=90011msec, maxt=90011msec
Disk stats (read/write):
vda: ios=4441/4488, merge=0/34, ticks=2965/8118, in_queue=11083,
util=11.64%
--------------------------------------------------
regards,
Edoardo Comar
WebSphere Application Service Platform for Networks (ASPN)
ecomar@xxxxxxxxxx
+44 (0)1962 81 5576
IBM UK Ltd, Hursley Park, SO21 2JN
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