From: Nitesh Shetty <nj.shetty@samsung.com>
Date: Tue, 13 Feb 2018 15:48:12 +0000 (+0530)
Subject: blk: optimization for classic polling
X-Git-Tag: v4.16-rc2~5^2~2
X-Git-Url: https://repo.jachan.dev/linux.git/commitdiff_plain/67b4110f8c8d16e588d7730db8e8b01b32c1bd8b

blk: optimization for classic polling

This removes the dependency on interrupts to wake up task. Set task
state as TASK_RUNNING, if need_resched() returns true,
while polling for IO completion.
Earlier, polling task used to sleep, relying on interrupt to wake it up.
This made some IO take very long when interrupt-coalescing is enabled in
NVMe.

Reference:
http://lists.infradead.org/pipermail/linux-nvme/2018-February/015435.html

Changes since v2->v3:
	-using __set_current_state() instead of set_current_state()

Changes since v1->v2:
	-setting task state once in blk_poll, instead of multiple
callers.

Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---

diff --git a/block/blk-mq.c b/block/blk-mq.c
index df93102e2149..357492712b0e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -3164,6 +3164,7 @@ static bool __blk_mq_poll(struct blk_mq_hw_ctx *hctx, struct request *rq)
 		cpu_relax();
 	}
 
+	__set_current_state(TASK_RUNNING);
 	return false;
 }