difference between "bandwidth (KB/s)" and "Bw (KB/s) mean"

[Lucian Grijincu <lucian@fb.com>]

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