From: Aaron Lu <aaron.lu@intel.com>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Jens Axboe <axboe@kernel.dk>, "Rafael J. Wysocki" <rjw@sisk.pl>,
James Bottomley <James.Bottomley@hansenpartnership.com>,
linux-pm@vger.kernel.org, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org, Aaron Lu <aaron.lwe@gmail.com>,
Shane Huang <shane.huang@amd.com>
Subject: Re: [PATCH v8 4/4] sd: change to auto suspend mode
Date: Fri, 1 Feb 2013 11:19:44 +0800 [thread overview]
Message-ID: <20130201031944.GA6960@aaronlu.sh.intel.com> (raw)
In-Reply-To: <Pine.LNX.4.44L0.1301311010200.1876-100000@iolanthe.rowland.org>
On Thu, Jan 31, 2013 at 10:13:05AM -0500, Alan Stern wrote:
> On Thu, 31 Jan 2013, Aaron Lu wrote:
>
> > > > +static int scsi_blk_runtime_suspend(struct device *dev)
> > > > +{
> > > > + struct scsi_device *sdev = to_scsi_device(dev);
> > >
> > > For this routine and the other new ones, it may be slightly more
> > > efficient to pass both dev and sdev as arguments (this depends on how
> > > smart the compiler's optimizer is). The caller already knows both of
> > > them, after all.
> >
> > What about passing only scsi_device? When device is needed, I can use
> > &sdev->sdev_gendev. Is this equally efficient?
>
> I don't know... The difference is very small in any case. The
> routines will probably be inlined automatically.
Indeed, I just checked the .s output of the three cases, they are all
the same. So we just need to care about readability and less of code,
passing only scsi_device seems to be the simplest, are you OK with this?
BTW, the compiler I used is gcc-4.7.2.
>
> > > > + if (sdev->request_queue->dev) {
> > > > + pm_runtime_mark_last_busy(dev);
> > > > + err = pm_runtime_autosuspend(dev);
> > > > + } else {
> > > > + err = pm_schedule_suspend(dev, 100);
> > > > + }
> > > > + } else {
> > > > err = pm_runtime_suspend(dev);
> > > > + }
> > > > return err;
> >
> > Shall we ignore the return value for these pm_xxx_suspend functions?
> > I mean we do not need to record the return value for them and return it,
> > since pm core doesn't care the return value of idle callback.
>
> Maybe it will care in a future kernel version. You might as well store
> the return code and pass it back.
OK.
Thanks,
Aaron
next prev parent reply other threads:[~2013-02-01 3:18 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-30 9:34 [PATCH v8 0/4] block layer runtime pm Aaron Lu
2013-01-30 9:34 ` [PATCH v8 1/4] block: add a flag to identify PM request Aaron Lu
2013-01-30 9:34 ` [PATCH v8 2/4] block: add runtime pm helpers Aaron Lu
2013-01-30 15:54 ` Alan Stern
2013-01-31 5:35 ` Aaron Lu
2013-01-31 15:09 ` Alan Stern
2013-01-30 9:34 ` [PATCH v8 3/4] block: implement runtime pm strategy Aaron Lu
2013-01-30 9:34 ` [PATCH v8 4/4] sd: change to auto suspend mode Aaron Lu
2013-01-30 15:38 ` Alan Stern
2013-01-31 5:43 ` Aaron Lu
2013-01-31 15:13 ` Alan Stern
2013-02-01 3:19 ` Aaron Lu [this message]
2013-02-01 15:11 ` Alan Stern
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20130201031944.GA6960@aaronlu.sh.intel.com \
--to=aaron.lu@intel.com \
--cc=James.Bottomley@hansenpartnership.com \
--cc=aaron.lwe@gmail.com \
--cc=axboe@kernel.dk \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-pm@vger.kernel.org \
--cc=linux-scsi@vger.kernel.org \
--cc=rjw@sisk.pl \
--cc=shane.huang@amd.com \
--cc=stern@rowland.harvard.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).