Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads

From	Mike Galbraith <efault@gmx.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads
Date	2017-07-31 22:00 +0200
Message-ID	<u9p17-1XO-5@gated-at.bofh.it> (permalink)
References	(1 earlier) <u7T3j-7P8-11@gated-at.bofh.it> <u8w4F-7n-1@gated-at.bofh.it> <u8Ykh-230-7@gated-at.bofh.it> <u9ep4-3Xg-3@gated-at.bofh.it> <u9nVo-1jR-19@gated-at.bofh.it>
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On Mon, 2017-07-31 at 14:41 -0400, Johannes Weiner wrote:
> 
> Adding an rq counter for tasks inside memdelay sections should be
> straight-forward as well (except for maybe the migration cost of that
> state between CPUs in ttwu that Mike pointed out).

What I pointed out should be easily eliminated (zero use case).
 
> That leaves the question of how to track these numbers per cgroup at
> an acceptable cost. The idea for a tree of cgroups is that walltime
> impact of delays at each level is reported for all tasks at or below
> that level. E.g. a leave group aggregates the state of its own tasks,
> the root/system aggregates the state of all tasks in the system; hence
> the propagation of the task state counters up the hierarchy.

The crux of the biscuit is where exactly the investment return lies.
 Gathering of these numbers ain't gonna be free, no matter how hard you
try, and you're plugging into paths where every cycle added is made of
userspace hide.

	-Mike

Thread

[PATCH 3/3] mm/sched: memdelay: memory health interface for systems and workloads Johannes Weiner <hannes@cmpxchg.org> - 2017-07-27 17:40 +0200
  Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Johannes Weiner <hannes@cmpxchg.org> - 2017-07-27 18:00 +0200
  Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Peter Zijlstra <peterz@infradead.org> - 2017-07-29 11:20 +0200
    Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Johannes Weiner <hannes@cmpxchg.org> - 2017-07-30 17:30 +0200
      Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Peter Zijlstra <peterz@infradead.org> - 2017-07-31 10:40 +0200
        Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Johannes Weiner <hannes@cmpxchg.org> - 2017-07-31 20:50 +0200
          Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Mike Galbraith <efault@gmx.de> - 2017-07-31 22:00 +0200
            Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Johannes Weiner <hannes@cmpxchg.org> - 2017-07-31 22:40 +0200
              Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Mike Galbraith <efault@gmx.de> - 2017-08-01 04:30 +0200
          Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Peter Zijlstra <peterz@infradead.org> - 2017-08-01 10:00 +0200
            Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads Johannes Weiner <hannes@cmpxchg.org> - 2017-08-01 14:30 +0200
  Re: [PATCH 3/3] mm/sched: memdelay: memory health interface for  systems and workloads kbuild test robot <lkp@intel.com> - 2017-07-29 15:40 +0200

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