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author | Ming Lei | 2017-10-14 17:22:29 +0800 |
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committer | Jens Axboe | 2017-11-01 08:20:02 -0600 |
commit | de1482974080ec9ef414bf048b2646b246b63f6e (patch) | |
tree | 3ecdc2b581a83848c43205c2fd9b6e97a6808f6a /kernel/audit.c | |
parent | 63ba8e31c3ac6393b07c6e18538814a730478766 (diff) |
blk-mq: introduce .get_budget and .put_budget in blk_mq_ops
For SCSI devices, there is often a per-request-queue depth, which needs
to be respected before queuing one request.
Currently blk-mq always dequeues the request first, then calls
.queue_rq() to dispatch the request to lld. One obvious issue with this
approach is that I/O merging may not be successful, because when the
per-request-queue depth can't be respected, .queue_rq() has to return
BLK_STS_RESOURCE, and then this request has to stay in hctx->dispatch
list. This means it never gets a chance to be merged with other IO.
This patch introduces .get_budget and .put_budget callback in blk_mq_ops,
then we can try to get reserved budget first before dequeuing request.
If the budget for queueing I/O can't be satisfied, we don't need to
dequeue request at all. Hence the request can be left in the IO
scheduler queue, for more merging opportunities.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'kernel/audit.c')
0 files changed, 0 insertions, 0 deletions