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SubjectRe: [PATCH] Fix delay accounting regression
Ingo Molnar wrote:
> * Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
>> Fix the delay accounting regression introduced by commit
>> 75d4ef16a6aa84f708188bada182315f80aab6fa. rq no longer has sched_info
>> data associated with it. task_struct sched_info structure is used by
>> delay accounting to provide back statistics to user space.
>
> no, this really is broken code. sched_clock() is not a generally
> reliable time source so at a minimum the rq->clock fix i mentioned is
> needed. What user-space tools are utilizing delay-accounting by the way?

Applications I can think of are

1. iotop
2. Some typical applications are mentioned in
https://ols2006.108.redhat.com/2007/Reprints/nagar-Reprint.pdf

> We have most of this data available under SCHEDSTATS - how about
> consolidating CONFIG_TASK_DELAY_ACCT into CONFIG_SCHEDSTATS?
>
> Ingo


Yes, we do use schedstats - except for two cases that I know of?

1. To accumulate information in taskstats to share with user space
(we copy the data from schedstats into taskstats)
2. We accumulate the data for dead threads in a thread group

--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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