Messages in this thread | | | Subject | Re: [PATCH] timers/nohz: Update nohz load even if tick already stopped | From | Scott Wood <> | Date | Fri, 08 Nov 2019 02:13:44 -0600 |
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On Tue, 2019-11-05 at 13:43 +0100, Peter Zijlstra wrote: > On Tue, Nov 05, 2019 at 01:30:58AM -0600, Scott Wood wrote: > > As for the warning in sched_tick_remote(), it seems like a test for time > > since the last tick on this cpu (remote or otherwise) would be better > > than > > relying on curr->se.exec_start, in order to detect things like this. > > I don't think we have a timestamp that is shared between the remote and > local tick.
Why wouldn't rq_clock_task() work on the local tick? It's what ->task_tick() itself uses.
> Also, there is a reason this warning uses the task time > accounting, there used to be (as in, I can't find it in a hurry) code > that could not deal with >u32 (~4s) clock updates.
Detecting a 3 second interval between ticks for a given cpu should assert in a superset of the situations the current check asserts in -- it just avoids the false negative of exec_runtime getting updated by something other than the tick.
-Scott
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