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Re: [PATCH 1/3] mm, sysctl: make VM stats configurable

From Dave Hansen <dave.hansen@linux.intel.com>
Newsgroups linux.kernel
Subject Re: [PATCH 1/3] mm, sysctl: make VM stats configurable
Date 2017-09-15 16:20 +0200
Message-ID <upZDj-3Xx-3@gated-at.bofh.it> (permalink)
References <upV6G-Sy-11@gated-at.bofh.it> <upV6G-Sy-15@gated-at.bofh.it> <upXrP-2iY-3@gated-at.bofh.it>
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On 09/15/2017 04:49 AM, Michal Hocko wrote:
> Why do we need an auto-mode? Is it safe to enforce by default.

Do we *need* it?  Not really.

But, it does offer the best of both worlds: The vast majority of users
see virtually no impact from the counters.  The minority that do need
them pay the cost *and* don't have to change their tooling at all.

> Is it> possible that userspace can get confused to see 0 NUMA stats in
the
> first read while other allocation stats are non-zero?

I doubt it.  Those counters are pretty worthless by themselves.  I have
tooling that goes and reads them, but it aways displays deltas.  Read
stats, sleep one second, read again, print the difference.

The only scenario I can see mattering is someone who is seeing a
performance issue due to NUMA allocation misses (or whatever) and wants
to go look *back* in the past.

A single-time printk could also go a long way to keeping folks from
getting confused.

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Thread

[PATCH 1/3] mm, sysctl: make VM stats configurable Kemi Wang <kemi.wang@intel.com> - 2017-09-15 11:30 +0200
  Re: [PATCH 1/3] mm, sysctl: make VM stats configurable Michal Hocko <mhocko@kernel.org> - 2017-09-15 14:00 +0200
    Re: [PATCH 1/3] mm, sysctl: make VM stats configurable Dave Hansen <dave.hansen@linux.intel.com> - 2017-09-15 16:20 +0200
      Re: [PATCH 1/3] mm, sysctl: make VM stats configurable Michal Hocko <mhocko@kernel.org> - 2017-09-15 16:30 +0200
        Re: [PATCH 1/3] mm, sysctl: make VM stats configurable kemi <kemi.wang@intel.com> - 2017-09-18 04:50 +0200
          Re: [PATCH 1/3] mm, sysctl: make VM stats configurable Michal Hocko <mhocko@kernel.org> - 2017-09-18 08:00 +0200
    RE: [PATCH 1/3] mm, sysctl: make VM stats configurable "Wang, Kemi" <kemi.wang@intel.com> - 2017-09-16 04:20 +0200
    Re: [PATCH 1/3] mm, sysctl: make VM stats configurable kemi <kemi.wang@intel.com> - 2017-09-18 05:30 +0200
      Re: [PATCH 1/3] mm, sysctl: make VM stats configurable Michal Hocko <mhocko@kernel.org> - 2017-09-18 08:00 +0200

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