On Fri, Mar 07, 2014 at 06:52:06PM -0800, Dan Williams wrote: > From: Dan Williams <dan.j.williams@xxxxxxxxx> > > async_schedule() sd resume work to allow disks and other devices to > resume in parallel. > > This moves the entirety of scsi_device resume to an async context to > ensure that scsi_device_resume() remains ordered with respect to the > completion of the start/stop command. For the duration of the resume, > new command submissions (that do not originate from the scsi-core) will > be deferred (BLKPREP_DEFER). > > It adds a new ASYNC_DOMAIN_EXCLUSIVE(scsi_sd_pm_domain) as a container > of these operations. Like scsi_sd_probe_domain it is flushed at > sd_remove() time to ensure async ops do not continue past the > end-of-life of the sdev. The implementation explicitly refrains from > reusing scsi_sd_probe_domain directly for this purpose as it is flushed > at the end of dpm_resume(), potentially defeating some of the benefit. > Given sdevs are quiesced it is permissible for these resume operations > to bleed past the async_synchronize_full() calls made by the driver > core. > > We defer the resolution of which pm callback to call until > scsi_dev_type_{suspend|resume} time and guarantee that the callback > parameter is never NULL. With this in place the type of resume > operation is encoded in the async function identifier. > > Inspired by Todd's analysis and initial proposal [2]: > https://01.org/suspendresume/blogs/tebrandt/2013/hard-disk-resume-optimization-simpler-approach The only thing which is a bit concerning is that this doesn't have any throttling mechanism for simultaneous wakeups. Would this be able to blow up the PSU if used on a machine with a lot of spindles? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html