diff options
| author | Jens Axboe <axboe@fb.com> | 2014-05-29 09:53:32 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2014-05-29 09:53:32 -0600 |
| commit | 05f1dd5315217398fc8d122bdee80f96a9f21274 (patch) | |
| tree | f1decfafa5f0d974d2f9c707a514bf68b9e2cddb /include | |
| parent | 4d92a9beb39d80a7d8ff7c04ae12a10290105ae5 (diff) | |
block: add queue flag for disabling SG merging
If devices are not SG starved, we waste a lot of time potentially
collapsing SG segments. Enough that 1.5% of the CPU time goes
to this, at only 400K IOPS. Add a queue flag, QUEUE_FLAG_NO_SG_MERGE,
which just returns the number of vectors in a bio instead of looping
over all segments and checking for collapsible ones.
Add a BLK_MQ_F_SG_MERGE flag so that drivers can opt-in on the sg
merging, if they so desire.
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/blk-mq.h | 1 | ||||
| -rw-r--r-- | include/linux/blkdev.h | 1 |
2 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 91dfb75ce39..95de239444d 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -129,6 +129,7 @@ enum { BLK_MQ_F_SHOULD_MERGE = 1 << 0, BLK_MQ_F_SHOULD_SORT = 1 << 1, BLK_MQ_F_TAG_SHARED = 1 << 2, + BLK_MQ_F_SG_MERGE = 1 << 3, BLK_MQ_S_STOPPED = 0, BLK_MQ_S_TAG_ACTIVE = 1, diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 098304576d5..695b9fd41ef 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -510,6 +510,7 @@ struct request_queue { #define QUEUE_FLAG_SAME_FORCE 18 /* force complete on same CPU */ #define QUEUE_FLAG_DEAD 19 /* queue tear-down finished */ #define QUEUE_FLAG_INIT_DONE 20 /* queue is initialized */ +#define QUEUE_FLAG_NO_SG_MERGE 21 /* don't attempt to merge SG segments*/ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_STACKABLE) | \ |