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block: attempt direct issue of plug list

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If we have just one queue type in the plug list, then we can extend our
direct issue to cover a full plug list as well. This allows sending a
batch of requests for direct issue, which is more efficient than doing
one-at-a-time kind of issue.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2021-10-19 06:02:30 -06:00
parent bc490f8173
commit dc5fc361d8
3 changed files with 62 additions and 0 deletions
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1
block/blk-core.c
View File

@ -1555,6 +1555,7 @@ void blk_start_plug_nr_ios(struct blk_plug *plug, unsigned short nr_ios)
plug->nr_ios = min_t(unsigned short, nr_ios, BLK_MAX_REQUEST_COUNT);
plug->rq_count = 0;
plug->multiple_queues = false;
plug->has_elevator = false;
plug->nowait = false;
INIT_LIST_HEAD(&plug->cb_list);

60
block/blk-mq.c
View File

@ -2149,6 +2149,58 @@ void blk_mq_insert_requests(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
spin_unlock(&ctx->lock);
}
static void blk_mq_commit_rqs(struct blk_mq_hw_ctx *hctx, int *queued,
bool from_schedule)
{
if (hctx->queue->mq_ops->commit_rqs) {
trace_block_unplug(hctx->queue, *queued, !from_schedule);
hctx->queue->mq_ops->commit_rqs(hctx);
}
*queued = 0;
}
static void blk_mq_plug_issue_direct(struct blk_plug *plug, bool from_schedule)
{
struct blk_mq_hw_ctx *hctx = NULL;
struct request *rq;
int queued = 0;
int errors = 0;
while ((rq = rq_list_pop(&plug->mq_list))) {
bool last = rq_list_empty(plug->mq_list);
blk_status_t ret;
if (hctx != rq->mq_hctx) {
if (hctx)
blk_mq_commit_rqs(hctx, &queued, from_schedule);
hctx = rq->mq_hctx;
}
ret = blk_mq_request_issue_directly(rq, last);
switch (ret) {
case BLK_STS_OK:
queued++;
break;
case BLK_STS_RESOURCE:
case BLK_STS_DEV_RESOURCE:
blk_mq_request_bypass_insert(rq, false, last);
blk_mq_commit_rqs(hctx, &queued, from_schedule);
return;
default:
blk_mq_end_request(rq, ret);
errors++;
break;
}
}
/*
* If we didn't flush the entire list, we could have told the driver
* there was more coming, but that turned out to be a lie.
*/
if (errors)
blk_mq_commit_rqs(hctx, &queued, from_schedule);
}
void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
{
struct blk_mq_hw_ctx *this_hctx;
@ -2160,6 +2212,12 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
return;
plug->rq_count = 0;
if (!plug->multiple_queues && !plug->has_elevator) {
blk_mq_plug_issue_direct(plug, from_schedule);
if (rq_list_empty(plug->mq_list))
return;
}
this_hctx = NULL;
this_ctx = NULL;
depth = 0;
@ -2376,6 +2434,8 @@ static void blk_add_rq_to_plug(struct blk_plug *plug, struct request *rq)
if (nxt && nxt->q != rq->q)
plug->multiple_queues = true;
}
if (!plug->has_elevator && (rq->rq_flags & RQF_ELV))
plug->has_elevator = true;
rq->rq_next = NULL;
rq_list_add(&plug->mq_list, rq);
plug->rq_count++;

1
include/linux/blkdev.h
View File

@ -737,6 +737,7 @@ struct blk_plug {
unsigned short rq_count;
bool multiple_queues;
bool has_elevator;
bool nowait;
struct list_head cb_list; /* md requires an unplug callback */