Messages in this thread | | | Date | Tue, 29 Jan 2013 17:06:20 +0800 | From | Yuanhan Liu <> | Subject | Re: aim7 performance regression by commit 5a50508 report from LKP |
| |
On Tue, Jan 29, 2013 at 09:44:00AM +0100, Ingo Molnar wrote: > > * Yuanhan Liu <yuanhan.liu@linux.intel.com> wrote: > > > [...] > > Very nice measurements and analysis, thanks! > > > As stated above, anybody can have a chance to own the lock in > > mutex once somebody release the lock. Well, there is only one > > to own the lock in rwsem write lock, and the one is known > > already: the one in the head of wait list. That would result > > to more contention in rwsem write lock case, especially if the > > one _will_ own the lock is not running now. > > I think we should allow lock-steal between rwsem writers - that > will not hurt fairness as most rwsem fairness concerns relate to > reader vs. writer fairness.
Agreed, and I'm sure this will improve performance and may make this performance regression go away.
David, is that Ok to you? If so, I may have a try.
> > Am I correct to assume that all relevant users in this workload > are down_write() users?
Yes, as commit 5a50508 just convert all mutex to down_write.
Thanks.
--yliu > > You can see the type of lock use in: > > perf record -g > perf report > > I bet that allowing rwsem writer lock-steal would improve other > workloads as well.
| |