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From: Jens Axboe <axboe@kernel.dk>
To: Hannes Reinecke <hare@suse.de>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/16] blk-mq: cache request hardware queue mapping
Date: Thu, 1 Nov 2018 06:22:14 -0600	[thread overview]
Message-ID: <5a12d8c2-cb16-168c-f8e2-ffe1649d6554@kernel.dk> (raw)
In-Reply-To: <222351ec-bf5b-526c-33dd-bd2e8ba051fa@suse.de>

On 11/1/18 3:27 AM, Hannes Reinecke wrote:
> On 10/30/18 7:32 PM, Jens Axboe wrote:
>> We call blk_mq_map_queue() a lot, at least two times for each
>> request per IO, sometimes more. Since we now have an indirect
>> call as well in that function. cache the mapping so we don't
>> have to re-call blk_mq_map_queue() for the same request
>> multiple times.
>>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
>> ---
>>   block/blk-flush.c      | 12 ++++--------
>>   block/blk-mq-debugfs.c |  4 +---
>>   block/blk-mq-sched.c   |  6 ++----
>>   block/blk-mq-tag.c     |  9 +--------
>>   block/blk-mq.c         | 22 +++++++++-------------
>>   block/blk-mq.h         |  5 +----
>>   include/linux/blkdev.h |  1 +
>>   7 files changed, 19 insertions(+), 40 deletions(-)
>>
> Hehe.
> I had been wondering about this since the original mq implementation, 
> but was told not to worry :-)

To be fair, it was just an array index. Now it's got an indirect
call, so it's more expensive.
 > Reviewed-by: Hannes Reinecke <hare@suse.com>

Thanks!

-- 
Jens Axboe


  reply	other threads:[~2018-11-01 12:22 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-30 18:32 [PATCHSET v3 0/16] blk-mq: Add support for multiple queue maps Jens Axboe
2018-10-30 18:32 ` [PATCH 01/16] blk-mq: kill q->mq_map Jens Axboe
2018-10-31  0:28   ` Sagi Grimberg
2018-10-30 18:32 ` [PATCH 02/16] blk-mq: abstract out queue map Jens Axboe
2018-10-31  0:31   ` Sagi Grimberg
2018-10-31 14:17     ` Jens Axboe
2018-10-30 18:32 ` [PATCH 03/16] blk-mq: provide dummy blk_mq_map_queue_type() helper Jens Axboe
2018-10-31  0:32   ` Sagi Grimberg
2018-10-30 18:32 ` [PATCH 04/16] blk-mq: pass in request/bio flags to queue mapping Jens Axboe
2018-10-31  0:37   ` Sagi Grimberg
2018-10-31 14:18     ` Jens Axboe
2018-10-30 18:32 ` [PATCH 05/16] blk-mq: allow software queue to map to multiple hardware queues Jens Axboe
2018-10-31  0:49   ` Sagi Grimberg
2018-10-31 14:19     ` Jens Axboe
2018-10-30 18:32 ` [PATCH 06/16] blk-mq: add 'type' attribute to the sysfs hctx directory Jens Axboe
2018-10-31  0:53   ` Sagi Grimberg
2018-10-31 14:21     ` Jens Axboe
2018-11-01 21:59   ` Omar Sandoval
2018-11-01 22:50     ` Jens Axboe
2018-10-30 18:32 ` [PATCH 07/16] blk-mq: support multiple hctx maps Jens Axboe
2018-10-31  0:59   ` Sagi Grimberg
2018-10-31 14:23     ` Jens Axboe
2018-10-30 18:32 ` [PATCH 08/16] blk-mq: separate number of hardware queues from nr_cpu_ids Jens Axboe
2018-10-31  1:00   ` Sagi Grimberg
2018-10-30 18:32 ` [PATCH 09/16] blk-mq: cache request hardware queue mapping Jens Axboe
2018-10-31  1:01   ` Sagi Grimberg
2018-11-01  9:27   ` Hannes Reinecke
2018-11-01 12:22     ` Jens Axboe [this message]
2018-10-30 18:32 ` [PATCH 10/16] blk-mq: cleanup and improve list insertion Jens Axboe
2018-10-31  1:03   ` Sagi Grimberg
2018-11-01  9:28   ` Hannes Reinecke
2018-10-30 18:32 ` [PATCH 11/16] blk-mq: improve plug list sorting Jens Axboe
2018-10-31  1:04   ` Sagi Grimberg
2018-11-01  9:30   ` Hannes Reinecke
2018-10-30 18:32 ` [PATCH 12/16] blk-mq: initial support for multiple queue maps Jens Axboe
2018-10-31  1:14   ` Sagi Grimberg
2018-10-30 18:32 ` [PATCH 13/16] irq: add support for allocating (and affinitizing) sets of IRQs Jens Axboe
2018-10-31  1:17   ` Sagi Grimberg
2018-11-02 14:37   ` Ming Lei
2018-11-02 15:09     ` Keith Busch
2018-11-03  2:22       ` Ming Lei
2018-10-30 18:32 ` [PATCH 14/16] nvme: utilize two queue maps, one for reads and one for writes Jens Axboe
2018-10-31  1:57   ` Sagi Grimberg
2018-10-31 14:32     ` Jens Axboe
2018-10-30 18:32 ` [PATCH 15/16] block: add REQ_HIPRI and inherit it from IOCB_HIPRI Jens Axboe
2018-10-31  1:58   ` Sagi Grimberg
2018-10-30 18:32 ` [PATCH 16/16] nvme: add separate poll queue map Jens Axboe
2018-10-30 18:35 ` [PATCHSET v3 0/16] blk-mq: Add support for multiple queue maps Keith Busch

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