From mboxrd@z Thu Jan 1 00:00:00 1970 From: Aaron Lu Subject: Re: [PATCH v8 4/4] sd: change to auto suspend mode Date: Fri, 1 Feb 2013 11:19:44 +0800 Message-ID: <20130201031944.GA6960@aaronlu.sh.intel.com> References: <20130131054324.GB14627@aaronlu.sh.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-pm-owner@vger.kernel.org To: Alan Stern Cc: Jens Axboe , "Rafael J. Wysocki" , James Bottomley , linux-pm@vger.kernel.org, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, Aaron Lu , Shane Huang List-Id: linux-scsi@vger.kernel.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