Messages in this thread Patch in this message | | | Date | Tue, 23 May 2006 11:23:24 +0200 | From | Jens Axboe <> | Subject | Re: wrong in_flight diskstat in 2.6.16.1 |
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On Tue, May 23 2006, Martin Devera wrote: > Hello, > > I see weird output from /sys/block/sd{a,b}/stat on our AMD64-X2 smp > machine with HT1000 (Broadcom) SATA with 2 WD 250GB HDDs in MD raid1. AS > scheduler was used, change to noop didn't change anything. It is vanilla > 2.6.16.1 and here are absolute values in hex and one second differences > below: > > 132CDF 56D62 61753C0 6966BC 165A8EB 5FF5B6C 3B32D6C0 1110594C FFCA89A4 > FEE85878 49FF74E4 > 132CDF 56D62 61753C0 6966BC 165A8EF 5FF5B6C 3B32D6E0 111059D0 FFCA89A1 > FEE85C60 79291244 > 0: 0 > 1: 0 > 2: 0 > 3: 0 > 4: 4 > 5: 0 > 6: 32 > 7: 132 > 8: -3 > 9: 1000 > 10: 791256416 > > As you can see in_flight is constantly negative and it is DECREASING > slowly all the time. > I can't find any reason for it :-\
Are you using io barriers?
[PATCH] blk: fix gendisk->in_flight accounting during barrier sequence
While executing barrrier sequence, the bar_rq which carries actual write was accounted as normal IO on completion, while it wasn't on queueing. This caused gendisk->in_flight to be decremented by 1 after each barrier thus messed up statistics.
This patch makes bar_rq not accounted as normal IO. As the containing barrier request as a whole is accounted, part of it shouldn't be.
Signed-off-by: Tejun Heo <htejun@gmail.com> Signed-off-by: Jens Axboe <axboe@suse.de>
diff --git a/block/ll_rw_blk.c b/block/ll_rw_blk.c index eac48be..7eb36c5 100644 --- a/block/ll_rw_blk.c +++ b/block/ll_rw_blk.c @@ -3452,7 +3452,12 @@ void end_that_request_last(struct reques if (unlikely(laptop_mode) && blk_fs_request(req)) laptop_io_completion(); - if (disk && blk_fs_request(req)) { + /* + * Account IO completion. bar_rq isn't accounted as a normal + * IO on queueing nor completion. Accounting the containing + * request is enough. + */ + if (disk && blk_fs_request(req) && req != &req->q->bar_rq) { unsigned long duration = jiffies - req->start_time; const int rw = rq_data_dir(req); -- Jens Axboe
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