Messages in this thread | | | From | Vincent Guittot <> | Date | Fri, 27 Jan 2023 17:18:56 +0100 | Subject | Re: [bug-report] possible s64 overflow in max_vruntime() |
| |
On Fri, 27 Jan 2023 at 12:44, Peter Zijlstra <peterz@infradead.org> wrote: > > On Thu, Jan 26, 2023 at 07:31:02PM +0100, Roman Kagan wrote: > > > > All that only matters for small sleeps anyway. > > > > > > Something like: > > > > > > sleep_time = U64_MAX; > > > if (se->avg.last_update_time) > > > sleep_time = cfs_rq_clock_pelt(cfs_rq) - se->avg.last_update_time; > > > > Interesting, why not rq_clock_task(rq_of(cfs_rq)) - se->exec_start, as > > others were suggesting? It appears to better match the notion of sleep > > wall-time, no? > > Should also work I suppose. cfs_rq_clock takes throttling into account, > but that should hopefully also not be *that* long, so either should > work.
yes rq_clock_task(rq_of(cfs_rq)) should be fine too
Another thing to take into account is the sleeper credit that the waking task deserves so the detection should be done once it has been subtracted from vruntime.
Last point, when a nice -20 task runs on a rq, it will take a bit more than 2 seconds for the vruntime to be increased by more than 24ms (the maximum credit that a waking task can get) so threshold must be significantly higher than 2 sec. On the opposite side, the lowest possible weight of a cfs rq is 2 which means that the problem appears for a sleep longer or equal to 2^54 = 2^63*2/1024. We should use this value instead of an arbitrary 200 days
| |