Messages in this thread Patch in this message | | | Date | Fri, 31 Oct 2008 13:47:44 +0100 | From | Jens Axboe <> | Subject | Re: disk statistics issue in 2.6.27 |
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On Thu, Oct 23 2008, Miquel van Smoorenburg wrote: > On Wed, 2008-10-22 at 19:17 +0200, Jens Axboe wrote: > > On Wed, Oct 22 2008, Miquel van Smoorenburg wrote: > > > On Mon, 2008-10-20 at 19:12 +0200, Jens Axboe wrote: > > > > On Sun, Oct 19 2008, Miquel van Smoorenburg wrote: > > > > > > > I noticed that the "iostat -k -x 2" output does't make any sense. > > > > > The number of reads/sec and number of writes/sec are about what I > > > > > would expect, and so are the other fields, but rkB/sec and wkB/sec > > > > > are completely off-scale: gigabytes read/written per second. > > > > > > > > > > > Are the reported values in iostat any sort of multiple of the real > > > > throughtput, or is is just insanely large? > > > > > > It looks like it's a multiple, but it appears to vary between 128 and > > > 512, and is different for reads and writes, so I do not know what to > > > make of it. > > > > > 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(); } -- Jens Axboe
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