On Tue, Jul 19, 2016 at 03:20:06PM -0700, Shaohua Li wrote: > On Fri, Jun 24, 2016 at 02:20:16PM +0200, Tomasz Majchrzak wrote: > > RAID10 random read performance is lower than expected due to excessive spinlock > > utilisation which is required mostly for rebuild/resync. Simplify allow_barrier > > as it's in IO path and encounters a lot of unnecessary congestion. > > > > As lower_barrier just takes a lock in order to decrement a counter, convert > > counter (nr_pending) into atomic variable and remove the spin lock. There is > > also a congestion for wake_up (it uses lock internally) so call it only when > > it's really needed. As wake_up is not called constantly anymore, ensure process > > waiting to raise a barrier is notified when there are no more waiting IOs. > > > > Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@xxxxxxxxx> > > Patch looks good, applied. Do you have data how this improves the performance? > > Thanks, > Shaohua I have tested it on a platform with 4 NVMe drives using fio random reads feature. Before the patch RAID10 array has been achieved 234% of single drive performance. With my patch the same array achieves 347% of single drive performance. The best performance of 4 drives in compare to one drive in this test could be 400% so it's around 30% boost. Tomek -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
