On Mon, 2013-01-21 at 17:22 +0800, Michael Wang wrote: > On 01/21/2013 05:09 PM, Mike Galbraith wrote: > > On Mon, 2013-01-21 at 15:45 +0800, Michael Wang wrote: > >> On 01/21/2013 03:09 PM, Mike Galbraith wrote: > >>> On Mon, 2013-01-21 at 07:42 +0100, Mike Galbraith wrote: > >>>> On Mon, 2013-01-21 at 13:07 +0800, Michael Wang wrote: > >>> > >>>>> May be we could try change this back to the old way later, after the aim > >>>>> 7 test on my server. > >>>> > >>>> Yeah, something funny is going on. > >>> > >>> Never entering balance path kills the collapse. Asking wake_affine() > >>> wrt the pull as before, but allowing us to continue should no idle cpu > >>> be found, still collapsed. So the source of funny behavior is indeed in > >>> balance_path. > >> > >> Below patch based on the patch set could help to avoid enter balance path > >> if affine_sd could be found, just like the old logical, would you like to > >> take a try and see whether it could help fix the collapse? > > > > No, it does not. > > Hmm...what have changed now compared to the old logical?
What I did earlier to confirm the collapse originates in balance_path is below. I just retested to confirm. Tasks jobs/min jti jobs/min/task real cpu 1 435.34 100 435.3448 13.92 3.76 Mon Jan 21 10:24:00 2013 1 440.09 100 440.0871 13.77 3.76 Mon Jan 21 10:24:22 2013 1 440.41 100 440.4070 13.76 3.75 Mon Jan 21 10:24:45 2013 5 2467.43 99 493.4853 12.28 10.71 Mon Jan 21 10:24:59 2013 5 2445.52 99 489.1041 12.39 10.98 Mon Jan 21 10:25:14 2013 5 2475.49 99 495.0980 12.24 10.59 Mon Jan 21 10:25:27 2013 10 4963.14 99 496.3145 12.21 20.64 Mon Jan 21 10:25:41 2013 10 4959.08 99 495.9083 12.22 21.26 Mon Jan 21 10:25:54 2013 10 5415.55 99 541.5550 11.19 11.54 Mon Jan 21 10:26:06 2013 20 9934.43 96 496.7213 12.20 33.52 Mon Jan 21 10:26:18 2013 20 9950.74 98 497.5369 12.18 36.52 Mon Jan 21 10:26:31 2013 20 9893.88 96 494.6939 12.25 34.39 Mon Jan 21 10:26:43 2013 40 18937.50 98 473.4375 12.80 84.74 Mon Jan 21 10:26:56 2013 40 18996.87 98 474.9216 12.76 88.64 Mon Jan 21 10:27:09 2013 40 19146.92 98 478.6730 12.66 89.98 Mon Jan 21 10:27:22 2013 80 37610.55 98 470.1319 12.89 112.01 Mon Jan 21 10:27:35 2013 80 37321.02 98 466.5127 12.99 114.21 Mon Jan 21 10:27:48 2013 80 37610.55 98 470.1319 12.89 111.77 Mon Jan 21 10:28:01 2013 160 69109.05 98 431.9316 14.03 156.81 Mon Jan 21 10:28:15 2013 160 69505.38 98 434.4086 13.95 155.33 Mon Jan 21 10:28:29 2013 160 69207.71 98 432.5482 14.01 155.79 Mon Jan 21 10:28:43 2013 320 108033.43 98 337.6045 17.95 314.01 Mon Jan 21 10:29:01 2013 320 108577.83 98 339.3057 17.86 311.79 Mon Jan 21 10:29:19 2013 320 108395.75 98 338.7367 17.89 312.55 Mon Jan 21 10:29:37 2013 640 151440.84 98 236.6263 25.61 620.37 Mon Jan 21 10:30:03 2013 640 151440.84 97 236.6263 25.61 621.23 Mon Jan 21 10:30:29 2013 640 151145.75 98 236.1652 25.66 622.35 Mon Jan 21 10:30:55 2013 1280 190117.65 98 148.5294 40.80 1228.40 Mon Jan 21 10:31:36 2013 1280 189977.96 98 148.4203 40.83 1229.91 Mon Jan 21 10:32:17 2013 1280 189560.12 98 148.0938 40.92 1231.71 Mon Jan 21 10:32:58 2013 2560 217857.04 98 85.1004 71.21 2441.61 Mon Jan 21 10:34:09 2013 2560 217338.19 98 84.8977 71.38 2448.76 Mon Jan 21 10:35:21 2013 2560 217795.87 97 85.0765 71.23 2443.12 Mon Jan 21 10:36:32 2013 That was with your change backed out, and the q/d below applied. --- kernel/sched/fair.c | 27 ++++++--------------------- 1 file changed, 6 insertions(+), 21 deletions(-) --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3337,6 +3337,8 @@ select_task_rq_fair(struct task_struct * goto unlock; if (sd_flag & SD_BALANCE_WAKE) { + new_cpu = prev_cpu; + /* * Tasks to be waked is special, memory it relied on * may has already been cached on prev_cpu, and usually @@ -3348,33 +3350,16 @@ select_task_rq_fair(struct task_struct * * from top to bottom, which help to reduce the chance in * some cases. */ - new_cpu = select_idle_sibling(p, prev_cpu); + new_cpu = select_idle_sibling(p, new_cpu); if (idle_cpu(new_cpu)) goto unlock; - /* - * No idle cpu could be found in the topology of prev_cpu, - * before jump into the slow balance_path, try search again - * in the topology of current cpu if it is the affine of - * prev_cpu. - */ - if (!sbm->affine_map[prev_cpu] || - !cpumask_test_cpu(cpu, tsk_cpus_allowed(p))) - goto balance_path; - - new_cpu = select_idle_sibling(p, cpu); - if (!idle_cpu(new_cpu)) - goto balance_path; + if (wake_affine(sbm->affine_map[cpu], p, sync)) + new_cpu = select_idle_sibling(p, cpu); - /* - * Invoke wake_affine() finally since it is no doubt a - * performance killer. - */ - if (wake_affine(sbm->affine_map[prev_cpu], p, sync)) - goto unlock; + goto unlock; } -balance_path: new_cpu = (sd_flag & SD_BALANCE_WAKE) ? prev_cpu : cpu; sd = sbm->sd[type][sbm->top_level[type]]; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/