The vast majority of time spent in S3 resume is consumed by the ATA subsystem as it resumes the computer's hard drives. For large hard disks this time can be upwards of 10 seconds, which makes S3 suspend/resume too costly to use frequently. This time needs to be reduced. More details here: https://01.org/suspendresume/blogs/tebrandt/2013/hard-disk-resume-worst-offender This patch set effectively reduces S3 resume time from multiple seconds to less than 700ms. The idea is to allow the ATA/SCSI subsystems to resume asynchronously without blocking system resume completion. The dpm_resume call currently waits for all asynchronous devices to finish resuming before it gives control back to the user. But in the case of ATA/SCSI we can give control back immediately, since the hard disks won't be needed immediately in lieu of RAM and cache. Patch 1/2 goes through and sets the power.async_suspend flag for every device in the ATA/SCSI resume path. This includes the ata port, link, and dev devices, the scsi host and target devices, all their associated transport devices, the block devices, and block partitions. This allows the entire ATA resume path to be added to the async device queue in drivers/base/power/main.c. Without this, the ATA resume path ends up in both queues (sync and async), which causes interdependencies and backs up the two queues. Patch 2/2 updates the drivers/base/power subsystem to allow any devices which have registred as asynchronous and who have not registered "complete" callbacks to be non-blocking. The ATA/SCSI subsystem devices don't register complete callbacks, so they automatically use the new feature. Testing was done with kernel 3.8.0-20.31_i386 and 3.8.0-20.31_amd64 Changelog: v2: - Updated patch submission. Incorporates comments from Tejun Heo. Fixed comment format, removed camelcase. No functional changes. block/genhd.c | 2 ++ block/partition-generic.c | 1 + drivers/ata/libata-transport.c | 4 +++- drivers/base/attribute_container.c | 1 + drivers/base/core.c | 7 ++++++- drivers/scsi/scsi_sysfs.c | 2 +- drivers/scsi/sd.c | 3 +++ drivers/base/power/main.c | 20 ++++++++++++++++---- 8 files changed, 33 insertions(+), 7 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
