* difference between "bandwidth (KB/s)" and "Bw (KB/s) mean"
[not found] <CBA3410B.13C2%lucian@fb.com>
@ 2012-04-05 20:23 ` Lucian Grijincu
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From: Lucian Grijincu @ 2012-04-05 20:23 UTC (permalink / raw)
To: fio@vger.kernel.org
I was expecting these two to be the same value.
You give this example in the HOWTO:
write: io= 32MB, bw= 666KB/s, iops=89 , runt= 50320msec
slat (msec): min= 0, max= 136, avg= 0.03, stdev= 1.92
clat (msec): min= 0, max= 631, avg=48.50, stdev=86.82
bw (KB/s) : min= 0, max= 1196, per=51.00%, avg=664.02, stdev=681.68
There's a small difference between them: 666KB/s vs 664.02KB/s
bw= Average bandwidth rate
bw=Bandwidth. Same names as the xlat stats, but also includes
an approximate percentage of total aggregate bandwidth
this thread received in this group. This last value is
slat=Submission latency (avg being the average, stdev being the
standard deviation).
From these descriptions I'd guess they are supposed to be the same value.
From tests I can see big differences between them (at least with
group_reporting):
- bandwidth (KB/s) - increases with number of threads and plateaus
- Bw (KB/s) mean - decreases with number of threads and plateaus
--
Lucian
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