Re: [PATCH v2] sched/fair: sanitize vruntime of entity being migrated

[Chen Yu]

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@xxxxxxxxxx>
> Signed-off-by: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
>
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@xxxxxxxxx/

thanks,
Chenyu