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From: Jens Axboe <axboe@kernel.dk>
To: Sagi Grimberg <sagi@grimberg.me>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 05/16] blk-mq: allow software queue to map to multiple hardware queues
Date: Wed, 31 Oct 2018 08:19:10 -0600	[thread overview]
Message-ID: <95e50d97-7cb3-7632-6e3f-b75ce32153ff@kernel.dk> (raw)
In-Reply-To: <f5bff9c7-2c94-8988-cf76-318fa0808cf0@grimberg.me>

On 10/30/18 6:49 PM, Sagi Grimberg wrote:
> 
> 
>> @@ -2342,10 +2346,16 @@ static void blk_mq_map_swqueue(struct request_queue *q)
>>   
>>   		ctx = per_cpu_ptr(q->queue_ctx, i);
>>   		hctx = blk_mq_map_queue_type(q, 0, i);
>> -
>> +		hctx->type = 0;
>>   		cpumask_set_cpu(i, hctx->cpumask);
>> -		ctx->index_hw = hctx->nr_ctx;
>> +		ctx->index_hw[hctx->type] = hctx->nr_ctx;
>>   		hctx->ctxs[hctx->nr_ctx++] = ctx;
>> +
>> +		/*
>> +		 * If the nr_ctx type overflows, we have exceeded the
>> +		 * amount of sw queues we can support.
>> +		 */
>> +		BUG_ON(!hctx->nr_ctx);
> 
> Was this added because nr_ctx became short? What was the motivation
> for that? save space? structure alignment?

Right, I made it smaller to not take up more space after this change.
And since it is now smaller, adding a check for wrap seemed like
a good idea.

> Perhaps this should be mentioned in the change log (as it contradicts
> that no functional changes exist in this patch). Or, if this can happen
> even when 32bit nr_ctx, it should be a separate small patch?

Could happen for any type, but more likely now of course. I'll
mention this in the changelog.

-- 
Jens Axboe


  reply	other threads:[~2018-10-31 14:19 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 [this message]
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
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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