| Message ID | 1444237232-9574-1-git-send-email-idryomov@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Fri, Oct 16, 2015 at 2:22 PM, Alex Elder <elder@ieee.org> wrote: > On 10/07/2015 12:00 PM, Ilya Dryomov wrote: >> Commit 30e2bc08b2bb ("Revert "block: remove artifical max_hw_sectors >> cap"") restored a clamp on max_sectors. It's now 2560 sectors instead >> of 1024, but it's not good enough: we set max_hw_sectors to rbd object >> size because we don't want object sized I/Os to be split, and the >> default object size is 4M. >> >> So, set max_sectors to max_hw_sectors in rbd at queue init time. >> >> Signed-off-by: Ilya Dryomov <idryomov@gmail.com> >> --- >> drivers/block/rbd.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c >> index 05072464d25e..04e69b4df664 100644 >> --- a/drivers/block/rbd.c >> +++ b/drivers/block/rbd.c >> @@ -3760,6 +3760,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) >> /* set io sizes to object size */ >> segment_size = rbd_obj_bytes(&rbd_dev->header); >> blk_queue_max_hw_sectors(q, segment_size / SECTOR_SIZE); >> + q->limits.max_sectors = queue_max_hw_sectors(q); > > This currently is done by default by blk_queue_max_hw_sectors(). > Do you see any different behavior with this patch in place? > > This change seems at least harmless so if it's not too late: Not quite. The commit mentioned above reintroduced this bit into blk_limits_max_hw_sectors() in 4.3-rc1: 241 limits->max_sectors = min_t(unsigned int, max_hw_sectors, 242 BLK_DEF_MAX_SECTORS); So this patch fixes a performance regression. If you spin up 4.3-rc1+ and map an rbd image without changing any settings, the best you'll see is 1280k I/Os despite a 4096k (typically) max_hw_sectors. Thanks, Ilya -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index 05072464d25e..04e69b4df664 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -3760,6 +3760,7 @@ static int rbd_init_disk(struct rbd_device *rbd_dev) /* set io sizes to object size */ segment_size = rbd_obj_bytes(&rbd_dev->header); blk_queue_max_hw_sectors(q, segment_size / SECTOR_SIZE); + q->limits.max_sectors = queue_max_hw_sectors(q); blk_queue_max_segments(q, segment_size / SECTOR_SIZE); blk_queue_max_segment_size(q, segment_size); blk_queue_io_min(q, segment_size);
Commit 30e2bc08b2bb ("Revert "block: remove artifical max_hw_sectors cap"") restored a clamp on max_sectors. It's now 2560 sectors instead of 1024, but it's not good enough: we set max_hw_sectors to rbd object size because we don't want object sized I/Os to be split, and the default object size is 4M. So, set max_sectors to max_hw_sectors in rbd at queue init time. Signed-off-by: Ilya Dryomov <idryomov@gmail.com> --- drivers/block/rbd.c | 1 + 1 file changed, 1 insertion(+)