Re: [PATCH] sched/cputime: Ensure correct utime and stime proportion

From: Xunlei Pang
Date: Wed Jul 04 2018 - 02:57:03 EST

On 7/2/18 11:21 PM, Tejun Heo wrote:
> Hello, Peter.
> On Tue, Jun 26, 2018 at 05:49:08PM +0200, Peter Zijlstra wrote:
>> Well, no, because the Changelog is incomprehensible and the patch
>> doesn't really have useful comments, so I'll have to reverse engineer
>> the entire thing, and I've just not had time for that.
> Just as an additional data point, we also sometimes see artifacts from
> cpu_adjust_time() in the form of per-task user or sys time getting
> stuck for some period (in extreme cases for over a minute) while the
> application isn't doing anything differently. We're telling the users
> that it's an inherent sampling artifact but it'd be nice to improve it
> if possible without adding noticeable overhead. No idea whether this
> patch's approach is a good one tho.

The patch has no noticeable overhead except the extra cputime fileds
added into task_struct. We've been running this patch on our servers
for months, looks good till now.