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From: Qais Yousef <qais.yousef@arm.com>
To: Vincent Guittot <vincent.guittot@linaro.org>
Cc: linux-kernel@vger.kernel.org, mingo@redhat.com,
	peterz@infradead.org, pauld@redhat.com,
	valentin.schneider@arm.com, srikar@linux.vnet.ibm.com,
	quentin.perret@arm.com, dietmar.eggemann@arm.com,
	Morten.Rasmussen@arm.com, hdanton@sina.com, parth@linux.ibm.com,
	riel@surriel.com
Subject: Re: [PATCH v4 11/11] sched/fair: rework find_idlest_group
Date: Wed, 20 Nov 2019 11:58:45 +0000	[thread overview]
Message-ID: <20191120115844.scli3gprgd5vvlt4@e107158-lin.cambridge.arm.com> (raw)
In-Reply-To: <1571405198-27570-12-git-send-email-vincent.guittot@linaro.org>

Hi Vincent

On 10/18/19 15:26, Vincent Guittot wrote:
> The slow wake up path computes per sched_group statisics to select the
> idlest group, which is quite similar to what load_balance() is doing
> for selecting busiest group. Rework find_idlest_group() to classify the
> sched_group and select the idlest one following the same steps as
> load_balance().
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---

LTP test has caught a regression in perf_event_open02 test on linux-next and I
bisected it to this patch.

That is checking out next-20191119 tag and reverting this patch on top the test
passes. Without the revert the test fails.

I think this patch disturbs this part of the test:

	https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/syscalls/perf_event_open/perf_event_open02.c#L209

When I revert this patch count_hardware_counters() returns a non zero value.
But with it applied it returns 0 which indicates that the condition terminates
earlier than what the test expects.

I'm failing to see the connection yet, but since I spent enough time bisecting
it I thought I'll throw this out before I continue to bottom it out in hope it
rings a bell for you or someone else.

The problem was consistently reproducible on Juno-r2.

LTP was compiled from 20190930 tag using

	./configure --host=aarch64-linux-gnu --prefix=~/arm64-ltp/
	make && make install



*** Output of the test when it fails ***

	# ./perf_event_open02 -v
	at iteration:0 value:254410384 time_enabled:195570320 time_running:156044100
	perf_event_open02    0  TINFO  :  overall task clock: 166935520
	perf_event_open02    0  TINFO  :  hw sum: 1200812256, task clock sum: 667703360
	hw counters: 300202518 300202881 300203246 300203611
	task clock counters: 166927400 166926780 166925660 166923520
	perf_event_open02    0  TINFO  :  ratio: 3.999768
	perf_event_open02    0  TINFO  :  nhw: 0.000100     /* I added this extra line for debug */
	perf_event_open02    1  TFAIL  :  perf_event_open02.c:370: test failed (ratio was greater than )



*** Output of the test when it passes (this patch reverted) ***

	# ./perf_event_open02 -v
	at iteration:0 value:300271482 time_enabled:177756080 time_running:177756080
	at iteration:1 value:300252655 time_enabled:166939100 time_running:166939100
	at iteration:2 value:300252877 time_enabled:166924920 time_running:166924920
	at iteration:3 value:300242545 time_enabled:166909620 time_running:166909620
	at iteration:4 value:300250779 time_enabled:166918540 time_running:166918540
	at iteration:5 value:300250660 time_enabled:166922180 time_running:166922180
	at iteration:6 value:258369655 time_enabled:167388920 time_running:143996600
	perf_event_open02    0  TINFO  :  overall task clock: 167540640
	perf_event_open02    0  TINFO  :  hw sum: 1801473873, task clock sum: 1005046160
	hw counters: 177971955 185132938 185488818 185488199 185480943 185477118 179657001 172499668 172137672 172139561
	task clock counters: 99299900 103293440 103503840 103502040 103499020 103496160 100224320 96227620 95999400 96000420
	perf_event_open02    0  TINFO  :  ratio: 5.998820
	perf_event_open02    0  TINFO  :  nhw: 6.000100     /* I added this extra line for debug */
	perf_event_open02    1  TPASS  :  test passed

Thanks

--
Qais Yousef

  parent reply	other threads:[~2019-11-20 11:58 UTC|newest]

Thread overview: 89+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18 13:26 [PATCH v4 00/10] sched/fair: rework the CFS load balance Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 01/11] sched/fair: clean up asym packing Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Clean " tip-bot2 for Vincent Guittot
2019-10-30 14:51   ` [PATCH v4 01/11] sched/fair: clean " Mel Gorman
2019-10-30 16:03     ` Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 02/11] sched/fair: rename sum_nr_running to sum_h_nr_running Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Rename sg_lb_stats::sum_nr_running " tip-bot2 for Vincent Guittot
2019-10-30 14:53   ` [PATCH v4 02/11] sched/fair: rename sum_nr_running " Mel Gorman
2019-10-18 13:26 ` [PATCH v4 03/11] sched/fair: remove meaningless imbalance calculation Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Remove " tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 04/11] sched/fair: rework load_balance Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Rework load_balance() tip-bot2 for Vincent Guittot
2019-10-30 15:45   ` [PATCH v4 04/11] sched/fair: rework load_balance Mel Gorman
2019-10-30 16:16     ` Valentin Schneider
2019-10-31  9:09     ` Vincent Guittot
2019-10-31 10:15       ` Mel Gorman
2019-10-31 11:13         ` Vincent Guittot
2019-10-31 11:40           ` Mel Gorman
2019-11-08 16:35             ` Vincent Guittot
2019-11-08 18:37               ` Mel Gorman
2019-11-12 10:58                 ` Vincent Guittot
2019-11-12 15:06                   ` Mel Gorman
2019-11-12 15:40                     ` Vincent Guittot
2019-11-12 17:45                       ` Mel Gorman
2019-11-18 13:50     ` Ingo Molnar
2019-11-18 13:57       ` Vincent Guittot
2019-11-18 14:51       ` Mel Gorman
2019-10-18 13:26 ` [PATCH v4 05/11] sched/fair: use rq->nr_running when balancing load Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Use " tip-bot2 for Vincent Guittot
2019-10-30 15:54   ` [PATCH v4 05/11] sched/fair: use " Mel Gorman
2019-10-18 13:26 ` [PATCH v4 06/11] sched/fair: use load instead of runnable load in load_balance Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Use load instead of runnable load in load_balance() tip-bot2 for Vincent Guittot
2019-10-30 15:58   ` [PATCH v4 06/11] sched/fair: use load instead of runnable load in load_balance Mel Gorman
2019-10-18 13:26 ` [PATCH v4 07/11] sched/fair: evenly spread tasks when not overloaded Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Spread out tasks evenly " tip-bot2 for Vincent Guittot
2019-10-30 16:03   ` [PATCH v4 07/11] sched/fair: evenly spread tasks " Mel Gorman
2019-10-18 13:26 ` [PATCH v4 08/11] sched/fair: use utilization to select misfit task Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Use " tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 09/11] sched/fair: use load instead of runnable load in wakeup path Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Use " tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 10/11] sched/fair: optimize find_idlest_group Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Optimize find_idlest_group() tip-bot2 for Vincent Guittot
2019-10-18 13:26 ` [PATCH v4 11/11] sched/fair: rework find_idlest_group Vincent Guittot
2019-10-21  9:12   ` [tip: sched/core] sched/fair: Rework find_idlest_group() tip-bot2 for Vincent Guittot
2019-10-22 16:46   ` [PATCH] sched/fair: fix rework of find_idlest_group() Vincent Guittot
2019-10-23  7:50     ` Chen, Rong A
2019-10-30 16:07     ` Mel Gorman
2019-11-18 17:42     ` [tip: sched/core] sched/fair: Fix " tip-bot2 for Vincent Guittot
2019-11-22 14:37     ` [PATCH] sched/fair: fix " Valentin Schneider
2019-11-25  9:16       ` Vincent Guittot
2019-11-25 11:03         ` Valentin Schneider
2019-11-20 11:58   ` Qais Yousef [this message]
2019-11-20 13:21     ` [PATCH v4 11/11] sched/fair: rework find_idlest_group Vincent Guittot
2019-11-20 16:53       ` Vincent Guittot
2019-11-20 17:34         ` Qais Yousef
2019-11-20 17:43           ` Vincent Guittot
2019-11-20 18:10             ` Qais Yousef
2019-11-20 18:20               ` Vincent Guittot
2019-11-20 18:27                 ` Qais Yousef
2019-11-20 19:28                   ` Vincent Guittot
2019-11-20 19:55                     ` Qais Yousef
2019-11-21 14:58                       ` Qais Yousef
2019-11-22 14:34   ` Valentin Schneider
2019-11-25  9:59     ` Vincent Guittot
2019-11-25 11:13       ` Valentin Schneider
2019-10-21  7:50 ` [PATCH v4 00/10] sched/fair: rework the CFS load balance Ingo Molnar
2019-10-21  8:44   ` Vincent Guittot
2019-10-21 12:56     ` Phil Auld
2019-10-24 12:38     ` Phil Auld
2019-10-24 13:46       ` Phil Auld
2019-10-24 14:59         ` Vincent Guittot
2019-10-25 13:33           ` Phil Auld
2019-10-28 13:03             ` Vincent Guittot
2019-10-30 14:39               ` Phil Auld
2019-10-30 16:24                 ` Dietmar Eggemann
2019-10-30 16:35                   ` Valentin Schneider
2019-10-30 17:19                     ` Phil Auld
2019-10-30 17:25                       ` Valentin Schneider
2019-10-30 17:29                         ` Phil Auld
2019-10-30 17:28                       ` Vincent Guittot
2019-10-30 17:44                         ` Phil Auld
2019-10-30 17:25                 ` Vincent Guittot
2019-10-31 13:57                   ` Phil Auld
2019-10-31 16:41                     ` Vincent Guittot
2019-10-30 16:24   ` Mel Gorman
2019-10-30 16:35     ` Vincent Guittot
2019-11-18 13:15     ` Ingo Molnar
2019-11-25 12:48 ` Valentin Schneider
2020-01-03 16:39   ` Valentin Schneider

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