Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race with cpuset update

From	Christoph Lameter <cl@linux.com>
Newsgroups	linux.kernel
Subject	Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race with cpuset update
Date	2017-05-17 16:00 +0200
Message-ID	<tI7EC-3KY-13@gated-at.bofh.it> (permalink)
References	(5 earlier) <tvGqt-7kR-5@gated-at.bofh.it> <twgaB-5Ia-1@gated-at.bofh.it> <tAql4-84y-15@gated-at.bofh.it> <tC4Jr-8ub-13@gated-at.bofh.it> <tI3rj-1fU-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, 17 May 2017, Michal Hocko wrote:

> > We certainly can do that. The failure of the page faults are due to the
> > admin trying to move an application that is not aware of this and is using
> > mempols. That could be an error. Trying to move an application that
> > contains both absolute and relative node numbers is definitely something
> > that is potentiall so screwed up that the kernel should not muck around
> > with such an app.
> >
> > Also user space can determine if the application is using memory policies
> > and can then take appropriate measures (message to the sysadmin to eval
> > tge situation f.e.) or mess aroud with the processes memory policies on
> > its own.
> >
> > So this is certainly a way out of this mess.
>
> So how are you going to distinguish VM_FAULT_OOM from an empty mempolicy
> case in a raceless way?

You dont have to do that if you do not create an empty mempolicy in the
first place. The current kernel code avoids that by first allowing access
to the new set of nodes and removing the old ones from the set when done.

Thread

Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Michal Hocko <mhocko@kernel.org> - 2017-05-17 11:30 +0200
  Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-17 16:00 +0200
    Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Michal Hocko <mhocko@kernel.org> - 2017-05-17 16:10 +0200
      Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-17 16:50 +0200
        Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Michal Hocko <mhocko@kernel.org> - 2017-05-17 17:00 +0200
          Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-17 17:30 +0200
          Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-17 17:30 +0200
            Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Michal Hocko <mhocko@kernel.org> - 2017-05-18 11:10 +0200
              Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-18 19:00 +0200
                Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Michal Hocko <mhocko@kernel.org> - 2017-05-18 19:30 +0200
                Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-18 21:10 +0200
                Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Michal Hocko <mhocko@kernel.org> - 2017-05-19 09:40 +0200
        Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race with  cpuset update Vlastimil Babka <vbabka@suse.cz> - 2017-05-18 12:10 +0200
          Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race  with cpuset update Christoph Lameter <cl@linux.com> - 2017-05-18 19:10 +0200
            Re: [RFC 1/6] mm, page_alloc: fix more premature OOM due to race with  cpuset update Vlastimil Babka <vbabka@suse.cz> - 2017-05-19 13:30 +0200

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