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authorMikulas Patocka <mpatocka@redhat.com>2011-01-13 19:59:47 +0000
committerAlasdair G Kergon <agk@redhat.com>2011-01-13 19:59:47 +0000
commitd9bf0b508ddfe19883b982b29a03c02ccbf53806 (patch)
tree815334dee3eabcf0cc35cd23928cc456c0212d2d /drivers/md
parent09c9d4c9b6a2b5909ae3c6265e4cd3820b636863 (diff)
downloadop-kernel-dev-d9bf0b508ddfe19883b982b29a03c02ccbf53806.zip
op-kernel-dev-d9bf0b508ddfe19883b982b29a03c02ccbf53806.tar.gz
dm io: remove BIO_RW_SYNCIO flag from kcopyd
Remove the REQ_SYNC flag to improve write throughput when writing to the origin with a snapshot on the same device (using the CFQ I/O scheduler). Sequential write throughput (chunksize of 4k, 32k, 512k) unpatched: 8.5, 8.6, 9.3 MB/s patched: 15.2, 18.5, 17.5 MB/s Snapshot exception reallocations are triggered by writes that are usually async, so mark the associated dm_io_request as async as well. This helps when using the CFQ I/O scheduler because it has separate queues for sync and async I/O. Async is optimized for throughput; sync for latency. With this change we're consciously favoring throughput over latency. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-kcopyd.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c
index d8587ba..5ad9231 100644
--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -345,7 +345,7 @@ static int run_io_job(struct kcopyd_job *job)
{
int r;
struct dm_io_request io_req = {
- .bi_rw = job->rw | REQ_SYNC | REQ_UNPLUG,
+ .bi_rw = job->rw | REQ_UNPLUG,
.mem.type = DM_IO_PAGE_LIST,
.mem.ptr.pl = job->pages,
.mem.offset = job->offset,
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