On Wed, 29 Apr 2015 11:31:09 +0200 Peter Zijlstra <[email protected]> wrote:
> On Wed, Apr 29, 2015 at 10:48:53AM +0800, Yuanhan Liu wrote: > > 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 <[email protected]> > > Cc: Peter Zijlstra <[email protected]> > > Signed-off-by: Yuanhan Liu <[email protected]> > > Thanks! > > Assuming you want to route this through Neil's MD tree: > > Acked-by: Peter Zijlstra (Intel) <[email protected]> Thanks a lot Peter! I've queued the three patches in my md tree for 4.2. Thanks yliu! NeilBrown > > > --- > > include/linux/wait.h | 13 +++++++++++++ > > 1 file changed, 13 insertions(+) > > > > diff --git a/include/linux/wait.h b/include/linux/wait.h > > index 2db8334..db78c72 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) > > -- > > 1.9.0 > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to [email protected] > More majordomo info at http://vger.kernel.org/majordomo-info.html
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