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

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Date:	Mon, 29 Jul 2013 08:08:09 -0600
From:	Jens Axboe <axboe@...nel.dk>
To:	Alexander Gordeev <agordeev@...hat.com>
CC:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>,
	James Bottomley <James.Bottomley@...senPartnership.com>,
	Mike Christie <michaelc@...wisc.edu>,
	Tejun Heo <tj@...nel.org>, 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 07/29/2013 05:18 AM, Alexander Gordeev wrote:
>> -static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap)
>> +static struct ata_queued_cmd *ata_qc_new(struct ata_port *ap,
>> +                                        struct scsi_cmnd *sc)
>>  {
>>         struct ata_queued_cmd *qc = NULL;
>> -       unsigned int i;
>> +       struct request *rq = sc->request;
>>  
>>         /* no command while frozen */
>>         if (unlikely(ap->pflags & ATA_PFLAG_FROZEN))
>>                 return NULL;
>>  
>> -       /* the last tag is reserved for internal command. */
>> -       for (i = 0; i < ATA_MAX_QUEUE - 1; i++)
> 
> blk-mq does not prevent tag ATA_TAG_INTERNAL from being using. Would it make
> sense to promote queue depth of length (ATA_MAX_QUEUE - 1) while always
> pointing ATA_TAG_INTERNAL to qcmd (see below)?

blk-mq does support a number of reserved tags, information just needs to
be passed in appropriately. So there is support for reserving X number
of error handling / emergency tags.

-- 
Jens Axboe

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