From mboxrd@z Thu Jan 1 00:00:00 1970 From: Phillip Susi Subject: Re: [PATCH 1/3] sd: don't bother spinning up disks on resume Date: Mon, 18 Nov 2013 10:54:22 -0500 Message-ID: <528A382E.10400@ubuntu.com> References: <527AF287.7020700@ubuntu.com> <927e15641f27b46f206f8ae8110201c8fd77b7e1.1383789225.git.psusi@ubuntu.com> <527BDA11.6060603@interlog.com> <527C0349.5010301@ubuntu.com> <1384626031.3614.7.camel@dabdike.int.hansenpartnership.com> <52883CE9.9040102@ubuntu.com> <1384670620.3614.24.camel@dabdike.int.hansenpartnership.com> <5288EBA6.3070609@ubuntu.com> <5289573A.9070307@interlog.com> <52896806.4040907@ubuntu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: Received: from cdptpa-omtalb.mail.rr.com ([75.180.132.120]:51584 "EHLO cdptpa-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751030Ab3KRPyY (ORCPT ); Mon, 18 Nov 2013 10:54:24 -0500 In-Reply-To: <52896806.4040907@ubuntu.com> Sender: linux-ide-owner@vger.kernel.org List-Id: linux-ide@vger.kernel.org To: dgilbert@interlog.com, James Bottomley Cc: todd.e.brandt@linux.intel.com, linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org, tj@kernel.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 11/17/2013 8:06 PM, Phillip Susi wrote: > I don't see anything particularly inefficient about issuing the > command in the eh path ( in fact, libata always uses the eh path to > handle power management ). You can of course, use the > manage_start_stop flag to have the disk start on resume if you > really want. Yikes, I think I see now why scsi eh is so bad: the entire host, not just the device is quiesced. I suppose now the question is how to issue the START STOP UNIT from sd_prep_fn()? I gather you can't just call scsi_execute_req() from there? Is there maybe a way to insert a START STOP UNIT request into the queue ahead of the current request being prepped? Can sd_prep_fn() be called concurrently on multiple cpus? Hrm.. what about TCQ? Would it be bad if the original request were queued ( to the drive ) before the START STOP UNIT command completed? -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.17 (MingW32) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJSijguAAoJEJrBOlT6nu75AlIH/3n1XFrWWjU2D209hwaBlRCu OHdAI40OUW0dqRrF7hyhH62X6SmDFG9pkZcCeZUNmSOEBtvkVjxJRv2VvpXpQL50 xXEiLCLukOYWG7krnVhD1BCrt9SfAjMsCpWmbC14m3epCWd9OQNFfU9vqU7mW18b 2NJPBukq+l8nzZtCl+8UMIQxH4RSkceJs3X7y4PhM65nN4kDMmJUABjJhHBZX30/ MQqu6pu2AW6Wf6SH0Sh1qIWfu45cIneuSDRP9qK5U/9902vhmGCLlt4zgbow8CQh muspp8A+bhcVQAJVdZvHz9gQMHS0dDRjLgBE23Yik0t+zBl0wvoFsaAG4BEi0lY= =6HCd -----END PGP SIGNATURE-----