linux-kernel - Re: [PATCH v12 0/5] block layer runtime pm

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Date:	Thu, 28 Mar 2013 16:54:35 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	James Bottomley <James.Bottomley@...senpartnership.com>
CC:	Jens Axboe <axboe@...nel.dk>,
	Alan Stern <stern@...land.harvard.edu>,
	"Rafael J. Wysocki" <rjw@...k.pl>, Tejun Heo <tj@...nel.org>,
	linux-pm@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Aaron Lu <aaron.lwe@...il.com>,
	Shane Huang <shane.huang@....com>,
	Oliver Neukum <oneukum@...e.de>
Subject: Re: [PATCH v12 0/5] block layer runtime pm

On 03/23/2013 12:23 PM, Jens Axboe wrote:
> On Sat, Mar 23 2013, Aaron Lu wrote:
>> In August 2010, Jens and Alan discussed about "Runtime PM and the block
>> layer". http://marc.info/?t=128259108400001&r=1&w=2
>> And then Alan has given a detailed implementation guide:
>> http://marc.info/?l=linux-scsi&m=133727953625963&w=2
>>
>> To test:
>> # ls -l /sys/block/sda
>> /sys/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/block/sda
>>
>> # echo 10000 > /sys/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/power/autosuspend_delay_ms
>> # echo auto > /sys/devices/pci0000:00/0000:00:1f.2/ata1/host0/target0:0:0/0:0:0:0/power/control
>> Then you'll see sda is suspended after 10secs idle.
>>
>> [ 1767.680192] sd 2:0:0:0: [sda] Synchronizing SCSI cache
>> [ 1767.680317] sd 2:0:0:0: [sda] Stopping disk
>>
>> And if you do some IO, it will resume immediately.
>> [ 1791.052438] sd 2:0:0:0: [sda] Starting disk
>>
>> For test, I often set the autosuspend time to 1 second. If you are using
>> a GUI, the 10 seconds delay may be too long that the disk can not enter
>> runtime suspended state.
>>
>> Note that sd's runtime suspend callback will dump some kernel messages
>> and the syslog daemon will write kernel message to /var/log/messages,
>> making the disk instantly resume after suspended. So for test, the
>> syslog daemon should better be temporarily stopped.
>>
>> A git repo for it, on top of block/for-next:
>> https://github.com/aaronlu/linux.git blockpm
>>
>> v12:
>> - Split patch 1 into 2 patches, one introduces REQ_PM in block layer
>>   and one uses that flag in SCSI layer, suggested by Jens Axboe.
> 
> Thanks Aaron, I've applied 1, and 3-4. I'll leave 2 and 5 for James to
> pickup. James, if you want me to carry them, just let me know.

Hi James,

May I know your opinion on the two SCSI patches in this series?

Thanks,
Aaron

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