linux-kernel - Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

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Message-ID: <52051033.8050605@kernel.dk>
Date:	Fri, 09 Aug 2013 09:52:19 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Alexander Gordeev <agordeev@...hat.com>
CC:	Tejun Heo <tj@...nel.org>,
	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Mike Christie <michaelc@...wisc.edu>,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Jeff Garzik <jgarzik@...ox.com>,
	linux-scsi <linux-scsi@...r.kernel.org>
Subject: Re: [PATCH RESEND 0/1] AHCI: Optimize interrupt processing

On 08/09/2013 09:07 AM, Alexander Gordeev wrote:
> On Fri, Aug 09, 2013 at 08:24:38AM -0600, Jens Axboe wrote:
>> On 08/09/2013 02:23 AM, Alexander Gordeev wrote:
>>> +	ap->qc_tags = blk_mq_init_tags(ATA_MAX_QUEUE, 1, NUMA_NO_NODE);
>>> +	if (!ap->qc_tags) {
>>> +		kfree(ap);
>>> +		return NULL;
>>> +	}
>>
>> This should be blk_mq_init_tags(ATA_MAX_QUEUE - 1, 1, ...) since the
>> total depth is normal_tags + reserved_tags.
> 
> Aha.. If blk_mq_init_tags() should be like this then?
> 
> diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
> index dcbc2a4..b131a48 100644
> --- a/block/blk-mq-tag.c
> +++ b/block/blk-mq-tag.c
> @@ -468,10 +468,9 @@ struct blk_mq_tags *blk_mq_init_tags(unsigned int nr_tags,
>  	 * Rest of the tags start at the queue list
>  	 */
>  	tags->nr_free = 0;
> -	while (nr_tags - tags->nr_reserved) {
> +	while (nr_tags--) {
>  		tags->freelist[tags->nr_free] = tags->nr_free +
>  							tags->nr_reserved;
> -		nr_tags--;
>  		tags->nr_free++;
>  	}

I misremembered, just checked the code. I think I used to have it like I
described, but changed it since I thought it would be more logical to
pass in full depth, and then what part of that is reserved. Looking at
the current code, your patch looks correct as-is.

-- 
Jens Axboe

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