Buffer read is counted as sync in rw_is_sync(). If we use it, blk_sq_make_request() will not do per-process plug any more.
I haven't changed blk_mq_make_request() yet. It makes sense to dispatch REQ_SYNC request immediately. But for buffer read, it's weird not to do per-process plug, as buffer read doesn't need low latency. blk_mq_merge_queue_io() isn't very helpful, as we don't have delay mechanism there, the queue is immediately flushed, which makes the merge very superficial. Signed-off-by: Shaohua Li <s...@fb.com> --- block/blk-mq.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index d5b4643..0ccbfac 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1106,7 +1106,7 @@ static struct request *blk_mq_map_request(struct request_queue *q, ctx = blk_mq_get_ctx(q); hctx = q->mq_ops->map_queue(q, ctx->cpu); - if (rw_is_sync(bio->bi_rw)) + if (bio->bi_rw & REQ_SYNC) rw |= REQ_SYNC; trace_block_getrq(q, bio, rw); @@ -1206,7 +1206,7 @@ static void blk_mq_make_request(struct request_queue *q, struct bio *bio) */ static void blk_sq_make_request(struct request_queue *q, struct bio *bio) { - const int is_sync = rw_is_sync(bio->bi_rw); + const int is_sync = !!(bio->bi_rw & REQ_SYNC); const int is_flush_fua = bio->bi_rw & (REQ_FLUSH | REQ_FUA); unsigned int use_plug, request_count = 0; struct blk_map_ctx data; -- 1.8.3.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/