diff options
| author | Denis V. Lunev <den@openvz.org> | 2015-05-12 17:30:55 +0300 |
|---|---|---|
| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2015-05-22 09:37:33 +0100 |
| commit | 4196d2f0308cb1ae13ed450424ab7dfe154acda9 (patch) | |
| tree | 144b613251246975ae7dd0033cd53a509a837c56 /block/io.c | |
| parent | eaf5fe2dd4ec001d645ff3b343f466457badaa64 (diff) | |
| download | qemu-4196d2f0308cb1ae13ed450424ab7dfe154acda9.tar.gz | |
block: minimal bounce buffer alignment
The patch introduces new concept: minimal memory alignment for bounce
buffers. Original so called "optimal" value is actually minimal required
value for aligment. It should be used for validation that the IOVec
is properly aligned and bounce buffer is not required.
Though, from the performance point of view, it would be better if
bounce buffer or IOVec allocated by QEMU will be aligned stricter.
The patch does not change any alignment value yet.
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1431441056-26198-2-git-send-email-den@openvz.org
CC: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block/io.c')
| -rw-r--r-- | block/io.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/block/io.c b/block/io.c index a05ad677d3..e6c363921d 100644 --- a/block/io.c +++ b/block/io.c @@ -201,8 +201,10 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp) } bs->bl.opt_transfer_length = bs->file->bl.opt_transfer_length; bs->bl.max_transfer_length = bs->file->bl.max_transfer_length; + bs->bl.min_mem_alignment = bs->file->bl.min_mem_alignment; bs->bl.opt_mem_alignment = bs->file->bl.opt_mem_alignment; } else { + bs->bl.min_mem_alignment = 512; bs->bl.opt_mem_alignment = 512; } @@ -221,6 +223,9 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp) bs->bl.opt_mem_alignment = MAX(bs->bl.opt_mem_alignment, bs->backing_hd->bl.opt_mem_alignment); + bs->bl.min_mem_alignment = + MAX(bs->bl.min_mem_alignment, + bs->backing_hd->bl.min_mem_alignment); } /* Then let the driver override it */ @@ -2489,7 +2494,7 @@ void *qemu_try_blockalign0(BlockDriverState *bs, size_t size) bool bdrv_qiov_is_aligned(BlockDriverState *bs, QEMUIOVector *qiov) { int i; - size_t alignment = bdrv_opt_mem_align(bs); + size_t alignment = bdrv_min_mem_align(bs); for (i = 0; i < qiov->niov; i++) { if ((uintptr_t) qiov->iov[i].iov_base % alignment) { |