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Date: Mon, 27 Jan 2014 08:59:12 -0800 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Fengguang Wu <fengguang.wu@...el.com> Cc: LKML <linux-kernel@...r.kernel.org> Subject: Re: [rcu] c0f4dfd4f9: -53% perf-stat.cpu-migrations On Fri, Jan 24, 2014 at 08:33:20PM +0800, Fengguang Wu wrote: > Hi Paul, > > Just FYI, we noticed -53% perf-stat.cpu-migrations in dd write tests > on btrfs, which looks good. First good commit is Nice! ;-) Thanx, Paul > commit c0f4dfd4f90f1667d234d21f15153ea09a2eaa66 > Author: Paul E. McKenney <paul.mckenney@...aro.org> > AuthorDate: Fri Dec 28 11:30:36 2012 -0800 > Commit: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> > 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 <paul.mckenney@...aro.org> > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> > > 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 majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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