linux-kernel - Re: [PATCH 1/2] don't wait on disk to start on resume

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Date:	Mon, 04 Feb 2013 22:27:44 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	"dbasehore ." <dbasehore@...omium.org>
CC:	Alan Stern <stern@...land.harvard.edu>,
	James Bottomley <JBottomley@...allels.com>,
	Jeff Garzik <jgarzik@...ox.com>, linux-ide@...r.kernel.org,
	linux-kernel <linux-kernel@...r.kernel.org>,
	SCSI development list <linux-scsi@...r.kernel.org>,
	Linux-pm mailing list <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 1/2] don't wait on disk to start on resume

On 02/04/2013 08:07 AM, dbasehore . wrote:
> On the topic that we do a fast return for both scsi and ata. Now I
> don't remember everything about this (and correct me if I'm wrong)
> since I figured this out a few months ago.
>
> There are some dependencies that scsi has on the resume path of ata. I
> think it's that before we can send the command to spin up the disk, we
> need to wait for the ata host controller to come up. As Aaron Lu
> pointed out, it takes seconds for the ata port to resume. On the hand,

I just did some more recording, the result is:
host controller takes 1ms or less to resume;
port reset takes the most time, almost the same as the whole port resume
callback, 2-4 seconds;
sd resume callback takes 16ms.

So for ata disks, the most time consuming part is in port's reset
routine, which is executed in port's resume callback.

-Aaron

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