Messages in this thread | | | Subject | Re: [PATCH] Fix /proc/stat freezes (was [PATCH v15] "task_isolation" mode) | From | Chris Metcalf <> | Date | Fri, 19 Aug 2016 21:42:19 -0400 |
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On 8/17/2016 3:37 PM, Christoph Lameter wrote: > On Tue, 16 Aug 2016, Chris Metcalf wrote: > >> - Dropped Christoph Lameter's patch to avoid scheduling the >> clocksource watchdog on nohz cores; the recommendation is to just >> boot with tsc=reliable for NOHZ in any case, if necessary. > We also said that there should be a WARN_ON if tsc=reliable is not > specified and processors are put into NOHZ mode. This is something not > obvious causing scheduling events on NOHZ processors.
Yes, I agree. Frederic said he would queue a patch to do that, so I didn't want to propose another patch that would conflict.
>> Frederic, do you have a sense of what is left to be done there? >> I can certainly try to contribute to that effort as well. > Here is a potential fix to the problem that /proc/stat values freeze when > processors go into NOHZ busy mode. I'd like to hear what people think > about the approach here. In particular one issue may be that I am > accessing remote tick-sched structures without serialization. But for > top/ps this may be ok. I noticed that other values shown by top/os also > sometime are a bit fuzzy.
This seems pretty plausible to me, but I'm not an expert on what kind of locking might be required for these data structures.
-- Chris Metcalf, Mellanox Technologies http://www.mellanox.com
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