| Message ID | 1496330073-51338-5-git-send-email-anton.nefedov@virtuozzo.com |
|---|---|
| State | New |
| Headers | show |
On 06/01/2017 10:14 AM, Anton Nefedov wrote: > From: "Denis V. Lunev" <den@openvz.org> > > Currently each single write operation can result in 3 write operations Maybe: Currently each single guest write operation can result in up to 3 host write operations > if guest offsets are not cluster aligned. One write is performed for the > real payload and two for COW-ed areas. Thus the data possibly lays > non-contiguously on the host filesystem. This will reduce further > sequential read performance significantly. > > The patch allocates the space in the file with cluster granularity, > ensuring > 1. better host offset locality > 2. less space allocation operations > (which can be expensive on distributed storage) > > Signed-off-by: Denis V. Lunev <den@openvz.org> > Signed-off-by: Anton Nefedov <anton.nefedov@virtuozzo.com> > --- > block/qcow2.c | 24 +++++++++++++++++++++++- > 1 file changed, 23 insertions(+), 1 deletion(-) > > diff --git a/block/qcow2.c b/block/qcow2.c > index b3ba5da..cd5efba 100644 > --- a/block/qcow2.c > +++ b/block/qcow2.c > @@ -1575,6 +1575,24 @@ fail: > return ret; > } > > +static void handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta) > +{ > + BDRVQcow2State *s = bs->opaque; > + QCowL2Meta *m; > + > + for (m = l2meta; m != NULL; m = m->next) { > + uint64_t bytes = m->nb_clusters << s->cluster_bits; > + > + if (m->cow_start.nb_bytes == 0 && m->cow_end.nb_bytes == 0) { > + continue; > + } > + > + /* try to alloc host space in one chunk for better locality */ > + bdrv_co_pwrite_zeroes(bs->file, m->alloc_offset, bytes, > + BDRV_REQ_ALLOCATE); Is it worth a trace point, to easily track when we are using handle_alloc_space()? Or do existing trace points in bdrv_co_pwrite_zeroes already sufficiently serve the purpose? > + } > +} > + > static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset, > uint64_t bytes, QEMUIOVector *qiov, > int flags) > @@ -1656,8 +1674,12 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset, > if (ret < 0) { > goto fail; > } > - > qemu_co_mutex_unlock(&s->lock); > + > + if (bs->file->bs->supported_zero_flags & BDRV_REQ_ALLOCATE) { > + handle_alloc_space(bs, l2meta); > + } > + This certainly looks better than v1! > BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); > trace_qcow2_writev_data(qemu_coroutine_self(), > cluster_offset + offset_in_cluster); >
diff --git a/block/qcow2.c b/block/qcow2.c index b3ba5da..cd5efba 100644 --- a/block/qcow2.c +++ b/block/qcow2.c @@ -1575,6 +1575,24 @@ fail: return ret; } +static void handle_alloc_space(BlockDriverState *bs, QCowL2Meta *l2meta) +{ + BDRVQcow2State *s = bs->opaque; + QCowL2Meta *m; + + for (m = l2meta; m != NULL; m = m->next) { + uint64_t bytes = m->nb_clusters << s->cluster_bits; + + if (m->cow_start.nb_bytes == 0 && m->cow_end.nb_bytes == 0) { + continue; + } + + /* try to alloc host space in one chunk for better locality */ + bdrv_co_pwrite_zeroes(bs->file, m->alloc_offset, bytes, + BDRV_REQ_ALLOCATE); + } +} + static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset, uint64_t bytes, QEMUIOVector *qiov, int flags) @@ -1656,8 +1674,12 @@ static coroutine_fn int qcow2_co_pwritev(BlockDriverState *bs, uint64_t offset, if (ret < 0) { goto fail; } - qemu_co_mutex_unlock(&s->lock); + + if (bs->file->bs->supported_zero_flags & BDRV_REQ_ALLOCATE) { + handle_alloc_space(bs, l2meta); + } + BLKDBG_EVENT(bs->file, BLKDBG_WRITE_AIO); trace_qcow2_writev_data(qemu_coroutine_self(), cluster_offset + offset_in_cluster);