Re: [bisected] commit: a9327cac440be4d8333bba975cbbf76045096275causes iostat output

[Jens Axboe]

On Sun, Oct 04 2009, Corrado Zoccolo wrote:
> Hi,
> with 2.6.32-rc1 I started getting the following strange output from
> "iostat -kx 2":
> Linux 2.6.31bisect (et2) 	04/10/2009 	_i686_	(2 CPU)
> 
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>           10,70    0,00    3,16   15,75    0,00   70,38
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> avgrq-sz avgqu-sz   await  svctm  %util
> sda              18,22     0,00    0,67    0,01    14,77     0,02
> 43,94     0,01   10,53 39043915,03 2629219,87
> sdb              60,89     9,68   50,79    3,04  1724,43    50,52
> 65,95     0,70   13,06 488437,47 2629219,87
> 
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            2,72    0,00    0,74    0,00    0,00   96,53
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> avgrq-sz avgqu-sz   await  svctm  %util
> sda               0,00     0,00    0,00    0,00     0,00     0,00
> 0,00     0,00    0,00   0,00 100,00
> sdb               0,00     0,00    0,00    0,00     0,00     0,00
> 0,00     0,00    0,00   0,00 100,00
> 
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            6,68    0,00    0,99    0,00    0,00   92,33
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> avgrq-sz avgqu-sz   await  svctm  %util
> sda               0,00     0,00    0,00    0,00     0,00     0,00
> 0,00     0,00    0,00   0,00 100,00
> sdb               0,00     0,00    0,00    0,00     0,00     0,00
> 0,00     0,00    0,00   0,00 100,00
> 
> avg-cpu:  %user   %nice %system %iowait  %steal   %idle
>            4,40    0,00    0,73    1,47    0,00   93,40
> 
> Device:         rrqm/s   wrqm/s     r/s     w/s    rkB/s    wkB/s
> avgrq-sz avgqu-sz   await  svctm  %util
> sda               0,00     0,00    0,00    0,00     0,00     0,00
> 0,00     0,00    0,00   0,00 100,00
> sdb               0,00     4,00    0,00    3,00     0,00    28,00
> 18,67     0,06   19,50 333,33 100,00
> 
> Global values for service time and utilization are garbage. For
> interval values, utilization is always 100%, and service time is
> higher than normal.
> 
> I bisected it down to:
> [a9327cac440be4d8333bba975cbbf76045096275] Seperate read and write
> statistics of in_flight requests
> and verified that reverting just that commit indeed solves the issue
> on 2.6.32-rc1.

I've reverted this commit since the next -rc is close, then we can debug
and potentially re-introduce this change after that. Thanks a lot for
reporting and bisecting it, too!

-- 
Jens Axboe

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