diff options
| author | Yuanhan Liu <yuanhan.liu@linux.intel.com> | 2015-05-08 18:19:05 +1000 |
|---|---|---|
| committer | NeilBrown <neilb@suse.de> | 2015-06-17 10:00:14 +1000 |
| commit | 9f3520c3115b451ac1301779fc3c769d94907a70 (patch) | |
| tree | 32aa25027053b7b97f741015573eda1df59ba28a | |
| parent | 4c9309c0cce96ea93be638dd243616e56e4bfe7d (diff) | |
wait: introduce wait_event_exclusive_cmd
It's just a variant of wait_event_cmd(), with exclusive flag being set.
For cases like RAID5, which puts many processes to sleep until 1/4
resources are free, a wake_up wakes up all processes to run, but
there is one process being able to get the resource as it's protected
by a spin lock. That ends up introducing heavy lock contentions, and
hurts performance badly.
Here introduce wait_event_exclusive_cmd to relieve the lock contention
naturally by letting wake_up just wake up one process.
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
v2: its assumed that wait*() and __wait*() have the same arguments - peterz
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>
| -rw-r--r-- | include/linux/wait.h | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h index 2db83349865b..db78c7204947 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -358,6 +358,19 @@ do { \ __ret; \ }) +#define __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2) \ + (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 1, 0, \ + cmd1; schedule(); cmd2) +/* + * Just like wait_event_cmd(), except it sets exclusive flag + */ +#define wait_event_exclusive_cmd(wq, condition, cmd1, cmd2) \ +do { \ + if (condition) \ + break; \ + __wait_event_exclusive_cmd(wq, condition, cmd1, cmd2); \ +} while (0) + #define __wait_event_cmd(wq, condition, cmd1, cmd2) \ (void)___wait_event(wq, condition, TASK_UNINTERRUPTIBLE, 0, 0, \ cmd1; schedule(); cmd2) |