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Re: [PATCH v2 0/5] mm: support parallel free of memory

From Michal Hocko <mhocko@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH v2 0/5] mm: support parallel free of memory
Date 2017-03-17 09:30 +0100
Message-ID <tlV7r-3m4-3@gated-at.bofh.it> (permalink)
References (2 earlier) <tljlx-1aZ-39@gated-at.bofh.it> <tljYd-1Jv-25@gated-at.bofh.it> <tloOe-55O-13@gated-at.bofh.it> <tlzzY-4tY-23@gated-at.bofh.it> <tlItA-2iT-7@gated-at.bofh.it>
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On Thu 16-03-17 11:36:21, Tim Chen wrote:
[...]
> Perhaps we can only do this expedited exit only when there are idle cpus around.
> We can use the root sched domain's overload indicator for such a quick check.

This is not so easy, I am afraid. Those CPUs might be idle for a good
reason (power saving etc.). You will never know by simply checking
one metric. This is why doing these optimistic parallelization
optimizations is far from trivial. This is not the first time somebody
wants to do this.  People are trying to make THP migration faster
doing the similar thing. I guess we really need a help from the
scheduler to do this properly, though. I've been thinking about an API
(e.g. try_to_run_in_backgroun) which would evaluate all these nasty
details and either return with -EBUSY or kick the background thread to
accomplish the work if the system is reasonably idle. I am not really
sure whether such an API is viable though.  Peter, what do you think?
-- 
Michal Hocko
SUSE Labs

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Thread

[PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-15 10:10 +0100
  [PATCH v2 2/5] mm: parallel free pages Aaron Lu <aaron.lu@intel.com> - 2017-03-15 10:10 +0100
    Re: [PATCH v2 2/5] mm: parallel free pages "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2017-03-15 10:50 +0100
      Re: [PATCH v2 2/5] mm: parallel free pages Aaron Lu <aaron.lu@intel.com> - 2017-03-15 13:00 +0100
  Re: [PATCH v2 0/5] mm: support parallel free of memory Michal Hocko <mhocko@kernel.org> - 2017-03-15 15:30 +0100
    Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-15 16:50 +0100
      Re: [PATCH v2 0/5] mm: support parallel free of memory Michal Hocko <mhocko@kernel.org> - 2017-03-15 17:30 +0100
        Re: [PATCH v2 0/5] mm: support parallel free of memory Tim Chen <tim.c.chen@linux.intel.com> - 2017-03-15 22:40 +0100
          Re: [PATCH v2 0/5] mm: support parallel free of memory Michal Hocko <mhocko@kernel.org> - 2017-03-16 10:10 +0100
            Re: [PATCH v2 0/5] mm: support parallel free of memory Tim Chen <tim.c.chen@linux.intel.com> - 2017-03-16 19:40 +0100
              Re: [PATCH v2 0/5] mm: support parallel free of memory Minchan Kim <minchan@kernel.org> - 2017-03-17 09:10 +0100
              Re: [PATCH v2 0/5] mm: support parallel free of memory Michal Hocko <mhocko@kernel.org> - 2017-03-17 09:30 +0100
                Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-17 13:40 +0100
                Re: [PATCH v2 0/5] mm: support parallel free of memory Michal Hocko <mhocko@kernel.org> - 2017-03-17 14:00 +0100
                Re: [PATCH v2 0/5] mm: support parallel free of memory Peter Zijlstra <peterz@infradead.org> - 2017-03-17 14:20 +0100
                Re: [PATCH v2 0/5] mm: support parallel free of memory Peter Zijlstra <peterz@infradead.org> - 2017-03-17 14:00 +0100
                Re: [PATCH v2 0/5] mm: support parallel free of memory Michal Hocko <mhocko@kernel.org> - 2017-03-17 14:30 +0100
            Re: [PATCH v2 0/5] mm: support parallel free of memory Dave Hansen <dave.hansen@intel.com> - 2017-03-21 16:10 +0100
              Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-22 09:20 +0100
              Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-24 08:10 +0100
            Re: [PATCH v2 0/5] mm: support parallel free of memory Tim Chen <tim.c.chen@linux.intel.com> - 2017-03-21 16:20 +0100
        Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-16 08:00 +0100
        Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-16 08:40 +0100
          Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-16 15:00 +0100
            Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-16 15:20 +0100
  Re: [PATCH v2 0/5] mm: support parallel free of memory Vlastimil Babka <vbabka@suse.cz> - 2017-03-15 16:00 +0100
    Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-15 17:00 +0100
    Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-17 04:20 +0100
  Re: [PATCH v2 0/5] mm: support parallel free of memory Aaron Lu <aaron.lu@intel.com> - 2017-03-17 03:30 +0100

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