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

[Peter Zijlstra]

On Thu, Mar 09, 2023 at 02:34:05PM +0100, Vincent Guittot wrote:

> Then, even if we don't clear exec_start before migrating and keep
> current value to be used in place_entity on the new cpu, we can't
> compare the rq_clock_task(rq_of(cfs_rq)) of 2 different rqs AFAICT

Blergh -- indeed, irq and steal time can skew them between CPUs :/
I suppose we can fudge that... wait_start (which is basically what we're
making it do) also does that IIRC.

I really dislike having this placement muck spreadout like proposed.

> side note, why do we reset exec_start ? Is it only to make task_hot
> returns false ?

Yeah, god aweful hack.