[PATCH v6 00/12] blk-mq: Implement runtime power management

Bart Van Assche
2018-08-09T19:41:37Z

Hello Jens,

This patch series not only implements runtime power management for blk-mq but
also fixes a starvation issue in the power management code for the legacy
block layer. Please consider this patch series for the upstream kernel.

Thanks,

Bart.

Changes compared to v5:
- Introduced a new flag RQF_DV that replaces RQF_PREEMPT for SCSI domain
validation.
- Introduced a new request queue state QUEUE_FLAG_DV_ONLY for SCSI domain
validation.
- Instead of using SDEV_QUIESCE for both runtime suspend and SCSI domain
validation, use that state for domain validation only and introduce a new
state for runtime suspend, namely SDEV_QUIESCE.
- Reallow system suspend during SCSI domain validation.
- Moved the runtime resume call from the request allocation code into
blk_queue_enter().
- Instead of relying on q_usage_counter, iterate over the tag set to determine
whether or not any requests are in flight.

Changes compared to v4:
- Dropped the patches "Give RQF_PREEMPT back its original meaning" and
"Serialize queue freezing and blk_pre_runtime_suspend()".
- Replaced "percpu_ref_read()" with "percpu_is_in_use()".
- Inserted pm_request_resume() calls in the block layer request allocation
code such that the context that submits a request no longer has to call
pm_runtime_get().

Changes compared to v3:
- Avoid adverse interactions between system-wide suspend/resume and runtime
power management by changing the PREEMPT_ONLY flag into a counter.
- Give RQF_PREEMPT back its original meaning, namely that it is only set for
ide_preempt requests.
- Remove the flag BLK_MQ_REQ_PREEMPT.
- Removed the pm_request_resume() call.

Changes compared to v2:
- Fixed the build for CONFIG_BLOCK=n.
- Added a patch that introduces percpu_ref_read() in the percpu-counter code.
- Added a patch that makes it easier to detect missing pm_runtime_get*() calls.
- Addressed Jianchao's feedback including the comment about runtime overhead
of switching a per-cpu counter to atomic mode.

Changes compared to v1:
- Moved the runtime power management code into a separate file.
- Addressed Ming's feedback.

Bart Van Assche (12):
block, scsi: Introduce request flag RQF_DV
scsi: Alter handling of RQF_DV requests
scsi: Only set RQF_DV for requests used for domain validation
scsi: Introduce the SDEV_SUSPENDED device status
block, scsi: Rename QUEUE_FLAG_PREEMPT_ONLY into DV_ONLY and introduce
PM_ONLY
scsi: Reallow SPI domain validation during system suspend
block: Move power management code into a new source file
block, scsi: Introduce blk_pm_runtime_exit()
block: Split blk_pm_add_request() and blk_pm_put_request()
block: Change the runtime power management approach (1/2)
block: Change the runtime power management approach (2/2)
blk-mq: Enable support for runtime power management

block/Kconfig | 5 +
block/Makefile | 1 +
block/blk-core.c | 310 ++++++------------------------
block/blk-mq-debugfs.c | 4 +-
block/blk-mq.c | 4 +-
block/blk-pm.c | 262 +++++++++++++++++++++++++
block/blk-pm.h | 69 +++++++
block/elevator.c | 22 +--
drivers/ide/ide-pm.c | 3 +-
drivers/scsi/scsi_lib.c | 266 ++++++++++++++++++-------
drivers/scsi/scsi_pm.c | 7 +-
drivers/scsi/scsi_sysfs.c | 2 +
drivers/scsi/scsi_transport_spi.c | 26 +--
drivers/scsi/sd.c | 10 +-
drivers/scsi/sr.c | 4 +-
include/linux/blk-mq.h | 6 +-
include/linux/blk-pm.h | 26 +++
include/linux/blkdev.h | 41 ++--
include/scsi/scsi_device.h | 15 +-
include/scsi/scsi_transport_spi.h | 1 -
20 files changed, 673 insertions(+), 411 deletions(-)
create mode 100644 block/blk-pm.c
create mode 100644 block/blk-pm.h
create mode 100644 include/linux/blk-pm.h

--
2.18.0