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Date:   Fri, 24 Mar 2023 12:05:29 +0800
From:   Chen Yu <yu.c.chen@intel.com>
To:     Vincent Guittot <vincent.guittot@linaro.org>
CC:     <mingo@redhat.com>, <peterz@infradead.org>,
        <juri.lelli@redhat.com>, <dietmar.eggemann@arm.com>,
        <rostedt@goodmis.org>, <bsegall@google.com>, <mgorman@suse.de>,
        <bristot@redhat.com>, <vschneid@redhat.com>,
        <linux-kernel@vger.kernel.org>, <zhangqiao22@huawei.com>,
        kernel test robot <yujie.liu@intel.com>
Subject: Re: [PATCH v2] sched/fair: sanitize vruntime of entity being migrated
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References: <20230317160810.107988-1-vincent.guittot@linaro.org>
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On 2023-03-17 at 17:08:10 +0100, Vincent Guittot wrote:
> Commit 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
> fixes an overflowing bug, but ignore a case that se->exec_start is reset
> after a migration.
> 
> For fixing this case, we delay the reset of se->exec_start after
> placing the entity which se->exec_start to detect long sleeping task.
> 
> In order to take into account a possible divergence between the clock_task
> of 2 rqs, we increase the threshold to around 104 days.
> 
> 
> Fixes: 829c1651e9c4 ("sched/fair: sanitize vruntime of entity being placed")
> Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
>
This patch has been confirmed by 0day to restore the performance which was decreased
by 829c1651e9c4[1], thanks for the fix.

commit:     a2e90611b9f425ad            829c1651e9c4a6f78398d3e6765          a53ce18cacb477dd0513c607f18

hackbench
throughput: 173811           -18.4%     141887                     +1.4%     176324

[1] https://lore.kernel.org/lkml/202303091155.672f546a-yujie.liu@intel.com/

thanks,
Chenyu