On Wed, 29 Oct 2014, Waiman Long wrote: > AIM7 XFS Disk Test (no overcommit) > kernel JPM Real Time Sys Time Usr Time > ----- --- --------- -------- -------- > PV ticketlock 2542373 7.08 98.95 5.44 > PV qspinlock 2549575 7.06 98.63 5.40 > unfairlock 2616279 6.91 97.05 5.42 > > AIM7 XFS Disk Test (200% overcommit) > kernel JPM Real Time Sys Time Usr Time > ----- --- --------- -------- -------- > PV ticketlock 644468 27.93 415.22 6.33 > PV qspinlock 645624 27.88 419.84 0.39 That number is made up by what? ----------------------------^^^^ > unfairlock 695518 25.88 377.40 4.09 > > AIM7 EXT4 Disk Test (no overcommit) > kernel JPM Real Time Sys Time Usr Time > ----- --- --------- -------- -------- > PV ticketlock 1995565 9.02 103.67 5.76 > PV qspinlock 2011173 8.95 102.15 5.40 > unfairlock 2066590 8.71 98.13 5.46 > > AIM7 EXT4 Disk Test (200% overcommit) > kernel JPM Real Time Sys Time Usr Time > ----- --- --------- -------- -------- > PV ticketlock 478341 37.63 495.81 30.78 > PV qspinlock 474058 37.97 475.74 30.95 > unfairlock 560224 32.13 398.43 26.27 > > For the AIM7 disk workload, both PV ticketlock and qspinlock have > about the same performance. The unfairlock performs slightly better > than the PV lock. Slightly? Taking the PV locks, which are basically the same for the existing ticket locks and your new fangled qlocks as a reference then the so called 'unfair locks' which are just the native locks w/o the PV nonsense are fundamentally better up to a whopping 18% in the ext4/200% overcommit case. See below. > EBIZZY-m Test (no overcommit) > kernel Rec/s Real Time Sys Time Usr Time > ----- ----- --------- -------- -------- > PV ticketlock 3255 10.00 60.65 3.62 > PV qspinlock 3318 10.00 54.27 3.60 > unfairlock 2833 10.00 26.66 3.09 > > EBIZZY-m Test (200% overcommit) > kernel Rec/s Real Time Sys Time Usr Time > ----- ----- --------- -------- -------- > PV ticketlock 841 10.00 71.03 2.37 > PV qspinlock 834 10.00 68.27 2.39 > unfairlock 865 10.00 27.08 1.51 > > futextest (no overcommit) > kernel kops/s > ----- ------ > PV ticketlock 11523 > PV qspinlock 12328 > unfairlock 9478 > > futextest (200% overcommit) > kernel kops/s > ----- ------ > PV ticketlock 7276 > PV qspinlock 7095 > unfairlock 5614 > > The ebizzy and futextest have much higher spinlock contention than > the AIM7 disk workload. In this case, the unfairlock performs worse > than both the PV ticketlock and qspinlock. The performance of the 2 > PV locks are comparable. While I can see that the PV lock stuff performs 13% better for the ebizzy no overcommit case, what about the very interresting numbers for the same test with 200% overcommit? The regular lock has a slightly better performance, but significantly less sys/usr time. How do you explain that? 'Lies, damned lies and statistics' comes to my mind. Thanks, tglx -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
