| Message ID | 29eb85e07efa8d2d360aa0ab952bff050a85ead5.1492026266.git.joseph.salisbury@canonical.com |
|---|---|
| State | New |
| Headers | show |
On 13/04/17 11:45, Joseph Salisbury wrote: > From: Ming Lei <ming.lei@canonical.com> > > BugLink: http://bugs.launchpad.net/bugs/1682215 > > If the last bvec of the 1st bio and the 1st bvec of the next > bio are physically contigious, and the latter can be merged > to last segment of the 1st bio, we should think they don't > violate sg gap(or virt boundary) limit. > > Both Vitaly and Dexuan reported lots of unmergeable small bios > are observed when running mkfs on Hyper-V virtual storage, and > performance becomes quite low. This patch fixes that performance > issue. > > The same issue should exist on NVMe, since it sets virt boundary too. > > Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com> > Reported-by: Dexuan Cui <decui@microsoft.com> > Tested-by: Dexuan Cui <decui@microsoft.com> > Cc: Keith Busch <keith.busch@intel.com> > Signed-off-by: Ming Lei <ming.lei@canonical.com> > Signed-off-by: Jens Axboe <axboe@fb.com> > (cherry picked from commit 729204ef49ec00b788ce23deb9eb922a5769f55d) > Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com> > --- > include/linux/blkdev.h | 22 +++++++++++++++++++++- > 1 file changed, 21 insertions(+), 1 deletion(-) > > diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h > index f28a95a..a0b6aae 100644 > --- a/include/linux/blkdev.h > +++ b/include/linux/blkdev.h > @@ -1387,6 +1387,25 @@ static inline bool bvec_gap_to_prev(struct request_queue *q, > return __bvec_gap_to_prev(q, bprv, offset); > } > > +/* > + * Check if the two bvecs from two bios can be merged to one segment. > + * If yes, no need to check gap between the two bios since the 1st bio > + * and the 1st bvec in the 2nd bio can be handled in one segment. > + */ > +static inline bool bios_segs_mergeable(struct request_queue *q, > + struct bio *prev, struct bio_vec *prev_last_bv, > + struct bio_vec *next_first_bv) > +{ > + if (!BIOVEC_PHYS_MERGEABLE(prev_last_bv, next_first_bv)) > + return false; > + if (!BIOVEC_SEG_BOUNDARY(q, prev_last_bv, next_first_bv)) > + return false; > + if (prev->bi_seg_back_size + next_first_bv->bv_len > > + queue_max_segment_size(q)) > + return false; > + return true; > +} > + > static inline bool bio_will_gap(struct request_queue *q, struct bio *prev, > struct bio *next) > { > @@ -1396,7 +1415,8 @@ static inline bool bio_will_gap(struct request_queue *q, struct bio *prev, > bio_get_last_bvec(prev, &pb); > bio_get_first_bvec(next, &nb); > > - return __bvec_gap_to_prev(q, &pb, nb.bv_offset); > + if (!bios_segs_mergeable(q, prev, &pb, &nb)) > + return __bvec_gap_to_prev(q, &pb, nb.bv_offset); > } > > return false; > Good test results, it's a clean cherry pick from upstream that has been around for a few months and hence given some testing upstream. Acked-by: Colin Ian King <colin.king@canonical.com>
On Thu, Apr 13, 2017 at 06:45:15AM -0400, Joseph Salisbury wrote: > From: Ming Lei <ming.lei@canonical.com> > > BugLink: http://bugs.launchpad.net/bugs/1682215 > > If the last bvec of the 1st bio and the 1st bvec of the next > bio are physically contigious, and the latter can be merged > to last segment of the 1st bio, we should think they don't > violate sg gap(or virt boundary) limit. > > Both Vitaly and Dexuan reported lots of unmergeable small bios > are observed when running mkfs on Hyper-V virtual storage, and > performance becomes quite low. This patch fixes that performance > issue. > > The same issue should exist on NVMe, since it sets virt boundary too. > > Reported-by: Vitaly Kuznetsov <vkuznets@redhat.com> > Reported-by: Dexuan Cui <decui@microsoft.com> > Tested-by: Dexuan Cui <decui@microsoft.com> > Cc: Keith Busch <keith.busch@intel.com> > Signed-off-by: Ming Lei <ming.lei@canonical.com> > Signed-off-by: Jens Axboe <axboe@fb.com> > (cherry picked from commit 729204ef49ec00b788ce23deb9eb922a5769f55d) > Signed-off-by: Joseph Salisbury <joseph.salisbury@canonical.com> Clean cherry pick, positive test results. Acked-by: Seth Forshee <seth.forshee@canonical.com>
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index f28a95a..a0b6aae 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1387,6 +1387,25 @@ static inline bool bvec_gap_to_prev(struct request_queue *q, return __bvec_gap_to_prev(q, bprv, offset); } +/* + * Check if the two bvecs from two bios can be merged to one segment. + * If yes, no need to check gap between the two bios since the 1st bio + * and the 1st bvec in the 2nd bio can be handled in one segment. + */ +static inline bool bios_segs_mergeable(struct request_queue *q, + struct bio *prev, struct bio_vec *prev_last_bv, + struct bio_vec *next_first_bv) +{ + if (!BIOVEC_PHYS_MERGEABLE(prev_last_bv, next_first_bv)) + return false; + if (!BIOVEC_SEG_BOUNDARY(q, prev_last_bv, next_first_bv)) + return false; + if (prev->bi_seg_back_size + next_first_bv->bv_len > + queue_max_segment_size(q)) + return false; + return true; +} + static inline bool bio_will_gap(struct request_queue *q, struct bio *prev, struct bio *next) { @@ -1396,7 +1415,8 @@ static inline bool bio_will_gap(struct request_queue *q, struct bio *prev, bio_get_last_bvec(prev, &pb); bio_get_first_bvec(next, &nb); - return __bvec_gap_to_prev(q, &pb, nb.bv_offset); + if (!bios_segs_mergeable(q, prev, &pb, &nb)) + return __bvec_gap_to_prev(q, &pb, nb.bv_offset); } return false;