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From:   Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To:     linux-block@vger.kernel.org, linux-kernel@vger.kernel.org
Cc:     Jens Axboe <axboe@kernel.dk>, Thomas Gleixner <tglx@linutronix.de>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Subject: [PATCH 2/3] blk-mq: Always complete remote completions requests in softirq
Date:   Sat, 23 Jan 2021 21:10:26 +0100
Message-Id: <20210123201027.3262800-3-bigeasy@linutronix.de>
In-Reply-To: <20210123201027.3262800-1-bigeasy@linutronix.de>
References: <20210123201027.3262800-1-bigeasy@linutronix.de>
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Controllers with multiple queues have their IRQ-handelers pinned to a
CPU. The core shouldn't need to complete the request on a remote CPU.

Remove this case and always raise the softirq to complete the request.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 block/blk-mq.c | 14 +-------------
 1 file changed, 1 insertion(+), 13 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f285a9123a8b0..90348ae518461 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -628,19 +628,7 @@ static void __blk_mq_complete_request_remote(void *dat=
a)
 {
 	struct request *rq =3D data;
=20
-	/*
-	 * For most of single queue controllers, there is only one irq vector
-	 * for handling I/O completion, and the only irq's affinity is set
-	 * to all possible CPUs.  On most of ARCHs, this affinity means the irq
-	 * is handled on one specific CPU.
-	 *
-	 * So complete I/O requests in softirq context in case of single queue
-	 * devices to avoid degrading I/O performance due to irqsoff latency.
-	 */
-	if (rq->q->nr_hw_queues =3D=3D 1)
-		blk_mq_trigger_softirq(rq);
-	else
-		rq->q->mq_ops->complete(rq);
+	blk_mq_trigger_softirq(rq);
 }
=20
 static inline bool blk_mq_complete_need_ipi(struct request *rq)
--=20
2.30.0