linux-kernel - [PATCH] block: remove WQ_POWER

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Date:	Wed, 11 Jun 2014 23:43:54 +0200
From:	Matias Bjørling <m@...rling.me>
To:	axboe@...nel.dk, linux-kernel@...r.kernel.org
Cc:	Matias Bjørling <m@...rling.me>
Subject: [PATCH] block: remove WQ_POWER_EFFICIENT from kblockd

blk-mq issues async requests through kblockd. To issue a work request on a
specific CPU, kblockd_schedule_delayed_work_on is used. However, the CPU can
change if the machine is a laptop or similar. In that case its
workqueue.power_efficient parameter is set to true. That enables kblockd to be
WQ_UNBOUND by default. Leaving blk-mq to bounce its hw ctx queues between CPUs.

Remove the kblockd WQ_POWER_EFFICIENT flag to prevent this behavior.

Signed-off-by: Matias Bjørling <m@...rling.me>
---
 block/blk-core.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index f6f6b9a..6f8dba1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3312,8 +3312,7 @@ int __init blk_dev_init(void)
 
 	/* used for unplugging and affects IO latency/throughput - HIGHPRI */
 	kblockd_workqueue = alloc_workqueue("kblockd",
-					    WQ_MEM_RECLAIM | WQ_HIGHPRI |
-					    WQ_POWER_EFFICIENT, 0);
+					    WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
 	if (!kblockd_workqueue)
 		panic("Failed to create kblockd\n");
 
-- 
1.9.1

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