| From | Vineeth Remanan Pillai <> | Subject | Re: [RFC PATCH v2 00/17] Core scheduling v2 | Date | Tue, 23 Apr 2019 18:45:27 +0000 |
| |
>> - Processes with different tags can still share the core
> I may have missed something... Could you explain this statement?
> This, to me, is the whole point of the patch series. If it's not > doing this then ... what?
What I meant was, the patch needs some more work to be accurate. There are some race conditions where the core violation can still happen. In our testing, we saw around 1 to 5% of the time being shared with incompatible processes. One example of this happening is as follows(let cpu 0 and 1 be siblings): - cpu 0 selects a process with a cookie - cpu 1 selects a higher priority process without cookie - Selection process restarts for cpu 0 and it might select a process with cookie but with lesser priority. - Since it is lesser priority, the logic in pick_next_task doesn't compare again for the cookie(trusts pick_task) and proceeds.
This is one of the scenarios that we saw from traces, but there might be other race conditions as well. Fix seems a little involved and We are working on that.
Thanks
|