Messages in this thread | | | Subject | Re: disk statistics issue in 2.6.27 | From | Miquel van Smoorenburg <> | Date | Mon, 03 Nov 2008 22:39:12 +0100 |
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On Fri, 2008-10-31 at 13:47 +0100, Jens Axboe wrote: > On Thu, Oct 23 2008, Miquel van Smoorenburg wrote: > > > I added some debug statements to block/blk-core.c, and it appears that > > blk_end_io() is always called with nr_bytes == 16320 Kbytes (16711680). > > > > Ofcourse I should have noticed earlier that iostat -x 2 always prints > > 32640 as "average request size" (in sectors). > > You didn't happen to log a backtrace from that, did you? That's a weird > nr_bytes, it's 0xff0000. > > I'm assuming this then fixes it, just wondering what the heck is going > on here. > > diff --git a/block/blk-core.c b/block/blk-core.c > index 33c8d4b..a372618 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -1712,11 +1710,12 @@ static int __end_that_request_first(struct request *req, int error, > if (blk_fs_request(req) && req->rq_disk) { > const int rw = rq_data_dir(req); > struct hd_struct *part; > - int cpu; > + int cpu, sectors; > > + sectors = min_t(int, nr_bytes >> 9, req->hard_nr_sectors); > cpu = part_stat_lock(); > part = disk_map_sector_rcu(req->rq_disk, req->sector); > - part_stat_add(cpu, part, sectors[rw], nr_bytes >> 9); > + part_stat_add(cpu, part, sectors[rw], sectors); > part_stat_unlock(); > }
I didn't try the above patch yet (it might work), but I did find the cause. I bisected the problem and it was caused by commit 427e59f09fdba387547106de7bab980b7fff77be , something in the scsi layer. More on linux-scsi (I'll Cc you)
Thanks
Mike.
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