diff options
| author | Mikulas Patocka <mpatocka@redhat.com> | 2011-01-13 19:59:47 +0000 |
|---|---|---|
| committer | Alasdair G Kergon <agk@redhat.com> | 2011-01-13 19:59:47 +0000 |
| commit | d9bf0b508ddfe19883b982b29a03c02ccbf53806 (patch) | |
| tree | 815334dee3eabcf0cc35cd23928cc456c0212d2d | |
| parent | 09c9d4c9b6a2b5909ae3c6265e4cd3820b636863 (diff) | |
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>
| -rw-r--r-- | drivers/md/dm-kcopyd.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/drivers/md/dm-kcopyd.c b/drivers/md/dm-kcopyd.c index d8587bac568..5ad9231c870 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, |