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SubjectRe: [bisected] commit: a9327cac440be4d8333bba975cbbf76045096275 causes iostat output
Date
On Monday 05 October 2009 00:36:53 Jens Axboe wrote:
> 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.
>

Thanks for reporting.

> 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!

Sorry. I missed converting to 2 seperate variables at

@@ -1030,7 +1030,7 @@ static void part_round_stats_single(int cpu, struct
hd_struct *part,
if (now == part->stamp)
return;

- if (part->in_flight) {
+ if (part_in_flight(part)) {
__part_stat_add(cpu, part, time_in_queue,
part_in_flight(part) * (now - part->stamp));
__part_stat_add(cpu, part, io_ticks, (now - part->stamp));

which caused this regression. I would post the patch with this fix included.

Thanks
Nikanth


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