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Date: Thu, 04 Sep 2008 20:42:03 +0800 From: Lin Ming <ming.m.lin@...el.com> To: Peter Zijlstra <a.p.zijlstra@...llo.nl> Cc: linux-kernel <linux-kernel@...r.kernel.org>, "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>, mingo <mingo@...e.hu>, Gregory Haskins <ghaskins@...ell.com> Subject: Re: oltp ~10% regression with 2.6.27-rc5 on stoakley machine On Thu, 2008-09-04 at 14:26 +0200, Peter Zijlstra wrote: > On Thu, 2008-09-04 at 20:12 +0800, Lin Ming wrote: > > > > > Thats bizarre... that just indicates the better clock, which should give > > > > > better (read fairer) scheduling hurts your workload. > > > > > > > > > > Is there anything I can run to see if we can fix the scheduler perhaps? > > > > > > > > I observed schedstats of sysbench, there's more > > > > "nr_failed_migrations_hot" > > > > > > > > 2.6.27-rc4: se.nr_failed_migrations_hot 11 > > > > 2.6.27-rc5: se.nr_failed_migrations_hot 95 > > > > > > > > task migration failed because of task_hot, the system is un-balanced? > > > > > > Ah, that makes sense, a more accurate clock could indeed make more tasks > > > hot. > > > > > > Can you try fiddling with: /proc/sys/kernel/sched_migration_cost ? > > > > sched_migration_cost regression > > ---------------------- ------------- > > 50000 ~6% > > 0 ~8% > > 500000 (default) ~10% > > 5000000 ~14% > > -1 ~19% > > at 50000 (~6%), is the predominant difference in schedstats still the > nr_failed_migrations_hot? Yes, it's strange that nr_failed_migrations_hot (cost=50000) is larger than (cost=500000) sched_migration_cost = 50000 ---------------------------------------------------------- se.exec_start : 3475158.689868 se.vruntime : 935215.526989 se.sum_exec_runtime : 14358.431942 se.avg_overlap : 0.000000 se.wait_start : 0.000000 se.sleep_start : 3475158.689868 se.block_start : 0.000000 se.sleep_max : 37.910779 se.block_max : 0.033796 se.exec_max : 0.121028 se.slice_max : 0.000000 se.wait_max : 6.007209 se.wait_sum : 25029.649588 se.wait_count : 1954948 sched_info.bkl_count : 0 se.nr_migrations : 2521 se.nr_migrations_cold : 0 se.nr_failed_migrations_affine : 0 se.nr_failed_migrations_running : 147 se.nr_failed_migrations_hot : 123 se.nr_forced_migrations : 0 se.nr_forced2_migrations : 1236 se.nr_wakeups : 1952827 se.nr_wakeups_sync : 1944785 se.nr_wakeups_migrate : 2479 se.nr_wakeups_local : 1930122 se.nr_wakeups_remote : 22705 se.nr_wakeups_affine : 13252 se.nr_wakeups_affine_attempts : 825950 se.nr_wakeups_passive : 0 se.nr_wakeups_idle : 0 avg_atom : 0.007355 avg_per_cpu : 5.695530 nr_switches : 1951994 nr_voluntary_switches : 1949963 nr_involuntary_switches : 2031 se.load.weight : 1024 policy : 0 prio : 120 clock-delta : 81 sched_migration_cost = 500000 ---------------------------------------------------------- se.exec_start : 3719706.806593 se.vruntime : 1049301.798712 se.sum_exec_runtime : 14636.764384 se.avg_overlap : 0.000121 se.wait_start : 0.000000 se.sleep_start : 3719706.806593 se.block_start : 0.000000 se.sleep_max : 214.989106 se.block_max : 0.036240 se.exec_max : 0.147829 se.slice_max : 0.000000 se.wait_max : 6.475864 se.wait_sum : 24932.530233 se.wait_count : 1922627 sched_info.bkl_count : 0 se.nr_migrations : 2314 se.nr_migrations_cold : 0 se.nr_failed_migrations_affine : 0 se.nr_failed_migrations_running : 71 se.nr_failed_migrations_hot : 76 se.nr_forced_migrations : 0 se.nr_forced2_migrations : 1735 se.nr_wakeups : 1920337 se.nr_wakeups_sync : 1908767 se.nr_wakeups_migrate : 2272 se.nr_wakeups_local : 1898194 se.nr_wakeups_remote : 22143 se.nr_wakeups_affine : 1218 se.nr_wakeups_affine_attempts : 820118 se.nr_wakeups_passive : 0 se.nr_wakeups_idle : 0 avg_atom : 0.007624 avg_per_cpu : 6.325308 nr_switches : 1919596 nr_voluntary_switches : 1917396 nr_involuntary_switches : 2200 se.load.weight : 1024 policy : 0 prio : 120 clock-delta : 69 -- 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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