block: queue work on power efficient wq

Block layer uses workqueues for multiple purposes. There is no real dependency
of scheduling these on the cpu which scheduled them.

On a idle system, it is observed that and idle cpu wakes up many times just to
service this work. It would be better if we can schedule it on a cpu which the
scheduler believes to be the most appropriate one.

This patch replaces normal workqueues with power efficient versions.

Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Tejun Heo <tj@kernel.org>

3 files changed, 12 insertions, 6 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 33c33bc99ddd..f0deb8bf89e1 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -3180,7 +3180,8 @@ int __init blk_dev_init(void)
 
         /* used for unplugging and affects IO latency/throughput - HIGHPRI */
         kblockd_workqueue = alloc_workqueue("kblockd",
-                                            WQ_MEM_RECLAIM | WQ_HIGHPRI, 0);
+                                            WQ_MEM_RECLAIM | WQ_HIGHPRI |
+                                            WQ_POWER_EFFICIENT, 0);
         if (!kblockd_workqueue)
                 panic("Failed to create kblockd\n");
 
diff --git a/block/blk-ioc.c b/block/blk-ioc.c
index 9c4bb8266bc8..4464c823cff2 100644
--- a/block/blk-ioc.c
+++ b/block/blk-ioc.c
@@ -144,7 +144,8 @@ void put_io_context(struct io_context *ioc)
         if (atomic_long_dec_and_test(&ioc->refcount)) {
                 spin_lock_irqsave(&ioc->lock, flags);
                 if (!hlist_empty(&ioc->icq_list))
-                        schedule_work(&ioc->release_work);
+                        queue_work(system_power_efficient_wq,
+                                        &ioc->release_work);
                 else
                         free_ioc = true;
                 spin_unlock_irqrestore(&ioc->lock, flags);
diff --git a/block/genhd.c b/block/genhd.c
index 20625eed5511..e9094b375c05 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1489,9 +1489,11 @@ static void __disk_unblock_events(struct gendisk *disk, bool check_now)
         intv = disk_events_poll_jiffies(disk);
         set_timer_slack(&ev->dwork.timer, intv / 4);
         if (check_now)
-                queue_delayed_work(system_freezable_wq, &ev->dwork, 0);
+                queue_delayed_work(system_freezable_power_efficient_wq,
+                                &ev->dwork, 0);
         else if (intv)
-                queue_delayed_work(system_freezable_wq, &ev->dwork, intv);
+                queue_delayed_work(system_freezable_power_efficient_wq,
+                                &ev->dwork, intv);
 out_unlock:
         spin_unlock_irqrestore(&ev->lock, flags);
 }
@@ -1534,7 +1536,8 @@ void disk_flush_events(struct gendisk *disk, unsigned int mask)
         spin_lock_irq(&ev->lock);
         ev->clearing |= mask;
         if (!ev->block)
-                mod_delayed_work(system_freezable_wq, &ev->dwork, 0);
+                mod_delayed_work(system_freezable_power_efficient_wq,
+                                &ev->dwork, 0);
         spin_unlock_irq(&ev->lock);
 }
 
@@ -1627,7 +1630,8 @@ static void disk_check_events(struct disk_events *ev,
 
         intv = disk_events_poll_jiffies(disk);
         if (!ev->block && intv)
-                queue_delayed_work(system_freezable_wq, &ev->dwork, intv);
+                queue_delayed_work(system_freezable_power_efficient_wq,
+                                &ev->dwork, intv);
 
         spin_unlock_irq(&ev->lock);