Hi Paul, Just FYI, we noticed -53% perf-stat.cpu-migrations in dd write tests on btrfs, which looks good. First good commit is
commit c0f4dfd4f90f1667d234d21f15153ea09a2eaa66 Author: Paul E. McKenney <[email protected]> AuthorDate: Fri Dec 28 11:30:36 2012 -0800 Commit: Paul E. McKenney <[email protected]> CommitDate: Tue Mar 26 08:04:51 2013 -0700 rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks Because RCU callbacks are now associated with the number of the grace period that they must wait for, CPUs can now take advance callbacks corresponding to grace periods that ended while a given CPU was in dyntick-idle mode. This eliminates the need to try forcing the RCU state machine while entering idle, thus reducing the CPU intensiveness of RCU_FAST_NO_HZ, which should increase its energy efficiency. Signed-off-by: Paul E. McKenney <[email protected]> Signed-off-by: Paul E. McKenney <[email protected]> Documentation/kernel-parameters.txt | 28 ++- include/linux/rcupdate.h | 1 + init/Kconfig | 17 +- kernel/rcutree.c | 28 +-- kernel/rcutree.h | 12 +- kernel/rcutree_plugin.h | 374 ++++++++++-------------------------- kernel/rcutree_trace.c | 2 - 7 files changed, 149 insertions(+), 313 deletions(-) b11cc5760a9c48c c0f4dfd4f90f1667d234d21f1 --------------- ------------------------- 86878 ~138% -90.3% 8397 ~152% cpuidle.POLL.time 154 ~16% -87.3% 19 ~55% cpuidle.POLL.usage 12177976 ~ 4% -85.6% 1748244 ~20% cpuidle.C1-NHM.time 381439 ~ 3% -68.4% 120538 ~ 2% softirqs.RCU 0.53 ~87% +161.8% 1.40 ~16% perf-profile.cpu-cycles.copy_user_generic_string.__btrfs_buffered_write.btrfs_file_aio_write.do_sync_write.vfs_write 5227241 ~ 4% -58.3% 2180928 ~ 7% cpuidle.C1E-NHM.time 0.67 ~88% +88.6% 1.26 ~21% perf-profile.cpu-cycles.calc_csum_metadata_size.btrfs_delalloc_release_metadata.btrfs_clear_bit_hook.clear_state_bit.clear_extent_bit 231531 ~ 2% -48.3% 119653 ~ 2% interrupts.LOC 91019 ~ 2% -40.2% 54404 ~ 2% cpuidle.C3-NHM.usage 1.991e+08 ~ 3% -36.7% 1.26e+08 ~ 7% cpuidle.C3-NHM.time 7.07 ~ 4% -32.7% 4.76 ~ 8% turbostat.%c3 23380 ~33% +41.2% 33024 ~ 6% proc-vmstat.kswapd_low_wmark_hit_quickly 62805 ~ 3% -28.4% 44960 ~ 2% softirqs.SCHED 64678 ~ 1% -30.1% 45195 ~ 1% softirqs.TIMER 55051 ~ 3% -22.2% 42823 ~ 2% interrupts.0:IO-APIC-edge.timer 920 ~ 4% +19.2% 1097 ~ 5% slabinfo.kmalloc-512.active_objs 920 ~ 4% +19.2% 1097 ~ 5% slabinfo.kmalloc-512.num_objs 361987 ~ 2% +9.9% 397730 ~ 0% cpuidle.C6-NHM.usage 5.30 ~ 1% -9.7% 4.78 ~ 1% turbostat.%c1 178105 ~ 3% -53.5% 82837 ~ 1% perf-stat.cpu-migrations 5763 ~ 8% -44.7% 3186 ~22% vmstat.system.cs 3566268 ~ 8% -44.8% 1968744 ~21% perf-stat.context-switches 658 ~ 2% -30.4% 458 ~ 0% vmstat.system.in 53376814 ~12% -24.2% 40482438 ~22% perf-stat.node-load-misses 2.996e+10 ~ 3% -10.8% 2.672e+10 ~ 3% perf-stat.L1-icache-load-misses 1.998e+09 ~ 4% -11.6% 1.766e+09 ~ 2% perf-stat.branch-misses 1.005e+12 ~ 5% -11.9% 8.852e+11 ~ 6% perf-stat.stalled-cycles-frontend 6.344e+08 ~ 2% -6.8% 5.915e+08 ~ 2% perf-stat.LLC-store-misses 2.892e+10 ~ 2% +5.4% 3.047e+10 ~ 3% perf-stat.bus-cycles perf-stat.cpu-migrations 90000 ++*----*----------*-*---*------*-----------------------------------+ * ** *.*.**.* * *.*.* **.*.*.*.* .*. | 80000 ++ *.* * | | | 70000 ++ | | | 60000 ++ | | | 50000 ++ | | | 40000 ++ | | O O | 30000 O+ O O O OO O O O O OO O O O OO O O O OO O O O O OO O O O OO O O | O | 20000 ++-----------------------------------------------------------------+ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
