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

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Message-ID: <1374790082.7397.1411.camel@haakon3.risingtidesystems.com>
Date:	Thu, 25 Jul 2013 15:08:02 -0700
From:	"Nicholas A. Bellinger" <nab@...ux-iscsi.org>
To:	Alexander Gordeev <agordeev@...hat.com>
Cc:	James Bottomley <James.Bottomley@...senPartnership.com>,
	Jens Axboe <axboe@...nel.dk>,
	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 Thu, 2013-07-25 at 12:16 +0200, Alexander Gordeev wrote:
> On Mon, Jul 22, 2013 at 02:10:36PM -0700, Nicholas A. Bellinger wrote:
> > Np.  FYI, you'll want to use the latest commit e7827b351 HEAD from
> > target-pending/scsi-mq, which now has functioning scsi-generic support.
> 
> Survives a boot, a kernel build and the build's result :)

Great.  Thanks for the feedback Alexander!

So the next step on my end is to enable -mq for ahci, and verify initial
correctness using QEMU/KVM hardware emulation.

Btw, I've been looking at enabling the SHT->cmd_size for struct
ata_queued_cmd descriptor pre-allocation, but AFAICT these descriptors
are already all pre-allocated by libata and obtained via ata_qc_new() ->
__ata_qc_from_tag() during ata_scsi_queuecmd().

So that said, with the struct request + struct scsi_cmnd pre-allocations
already provided by blk-mq -> scsi-mq code, all memory allocations
should have already been eliminated from I/O fast path.

--nab

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