linux-kernel - [PATCH] blk-mq: Reuse hardware context cpumask for tags

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Date:	Wed,  2 Dec 2015 16:57:06 +0530
From:	Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
To:	<axboe@...nel.dk>
Cc:	<tom.leiming@...il.com>, <linux-block@...r.kernel.org>,
	<jmoyer@...hat.com>, <akinobu.mita@...il.com>,
	<nacc@...ux.vnet.ibm.com>, <linux-kernel@...r.kernel.org>,
	<raghavendra.kt@...ux.vnet.ibm.com>
Subject: [PATCH] blk-mq: Reuse hardware context cpumask for tags

hctx->cpumask is already populated and let the tag cpumask follow that
instead of going through a new for loop.

Signed-off-by: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com>
---
 block/blk-mq.c | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

 Nish had suggested to put cpumask_copy after WARN_ON (instead of before).

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 6d6f8fe..6ada3b4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1854,6 +1854,7 @@ static void blk_mq_map_swqueue(struct request_queue *q,
 		hctx->tags = set->tags[i];
 		WARN_ON(!hctx->tags);
 
+		cpumask_copy(hctx->tags->cpumask, hctx->cpumask);
 		/*
 		 * Set the map size to the number of mapped software queues.
 		 * This is more accurate and more efficient than looping
@@ -1867,14 +1868,6 @@ static void blk_mq_map_swqueue(struct request_queue *q,
 		hctx->next_cpu = cpumask_first(hctx->cpumask);
 		hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
 	}
-
-	queue_for_each_ctx(q, ctx, i) {
-		if (!cpumask_test_cpu(i, online_mask))
-			continue;
-
-		hctx = q->mq_ops->map_queue(q, i);
-		cpumask_set_cpu(i, hctx->tags->cpumask);
-	}
 }
 
 static void queue_set_hctx_shared(struct request_queue *q, bool shared)
-- 
1.7.11.7

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