Re: [RFC PATCH 3/3] mm: increase scalability of global memory commitment accounting

From	Andrew Morton <akpm@linux-foundation.org>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH 3/3] mm: increase scalability of global memory commitment accounting
Date	2016-02-11 22:00 +0100
Message-ID	<r16vg-5ys-9@gated-at.bofh.it> (permalink)
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On Wed, 10 Feb 2016 16:24:16 -0800 Tim Chen <tim.c.chen@linux.intel.com> wrote:

> On Wed, 2016-02-10 at 13:28 -0800, Andrew Morton wrote:
> 
> > 
> > If a process is unmapping 4MB then it's pretty crazy for us to be
> > hitting the percpu_counter 32 separate times for that single operation.
> > 
> > Is there some way in which we can batch up the modifications within the
> > caller and update the counter less frequently?  Perhaps even in a
> > single hit?
> 
> I think the problem is the batch size is too small and we overflow
> the local counter into the global counter for 4M allocations.

That's one way of looking at the issue.  The other way (which I point
out above) is that we're calling vm_[un]_acct_memory too frequently
when mapping/unmapping 4M segments.

Exactly which mmap.c callsite is causing this issue?

Thread

[RFC PATCH 3/3] mm: increase scalability of global memory commitment accounting Andrey Ryabinin <aryabinin@virtuozzo.com> - 2016-02-10 16:00 +0100
  Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Konstantin Khlebnikov <koct9i@gmail.com> - 2016-02-10 18:50 +0100
    Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Andrey Ryabinin <aryabinin@virtuozzo.com> - 2016-02-11 14:40 +0100
      Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Tim Chen <tim.c.chen@linux.intel.com> - 2016-02-11 18:10 +0100
  Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Tim Chen <tim.c.chen@linux.intel.com> - 2016-02-10 19:10 +0100
    Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Andrew Morton <akpm@linux-foundation.org> - 2016-02-10 22:30 +0100
      Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Tim Chen <tim.c.chen@linux.intel.com> - 2016-02-11 01:30 +0100
        Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Andrey Ryabinin <aryabinin@virtuozzo.com> - 2016-02-11 15:00 +0100
          Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Tim Chen <tim.c.chen@linux.intel.com> - 2016-02-11 19:30 +0100
            Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Dave Hansen <dave@sr71.net> - 2016-02-11 20:50 +0100
        Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Andrew Morton <akpm@linux-foundation.org> - 2016-02-11 22:00 +0100
          Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Tim Chen <tim.c.chen@linux.intel.com> - 2016-02-11 22:20 +0100
          Re: [RFC PATCH 3/3] mm: increase scalability of global memory  commitment accounting Andrey Ryabinin <aryabinin@virtuozzo.com> - 2016-02-12 13:30 +0100

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