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Groups > linux.kernel > #1666329

Re: Sleeping BUG in khugepaged for i586

From David Rientjes <rientjes@google.com>
Newsgroups linux.kernel
Subject Re: Sleeping BUG in khugepaged for i586
Date 2017-06-15 02:30 +0200
Message-ID <tSqPE-3IL-7@gated-at.bofh.it> (permalink)
References (6 earlier) <tQcnM-z9-9@gated-at.bofh.it> <tQAJs-7ia-21@gated-at.bofh.it> <tQJD4-4zr-9@gated-at.bofh.it> <tRksV-2Q5-3@gated-at.bofh.it> <tRr1n-6ZK-5@gated-at.bofh.it>
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On Mon, 12 Jun 2017, Michal Hocko wrote:

> > These are not soft lockups, these are need_resched warnings.  We monitor 
> > how long need_resched has been set and when a thread takes an excessive 
> > amount of time to reschedule after it has been set.  A loop of 512 pages 
> > with ptl contention and doing {clear,copy}_user_highpage() shows that 
> > need_resched can sit without scheduling for an excessive amount of time.
> 
> How much is excessive here?

We monitor anything that holds the cpu for more than 1/20th of a second, 
but this specific occurrence has been observed for ~1/8th.  The majority 
of mm/ is quite good in this regard.

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Thread

Re: Sleeping BUG in khugepaged for i586 David Rientjes <rientjes@google.com> - 2017-06-07 23:00 +0200
  Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-08 16:50 +0200
    Re: Sleeping BUG in khugepaged for i586 Matthew Wilcox <willy@infradead.org> - 2017-06-08 19:10 +0200
      Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-08 22:20 +0200
        Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-08 22:40 +0200
          Re: Sleeping BUG in khugepaged for i586 Vlastimil Babka <vbabka@suse.cz> - 2017-06-09 08:50 +0200
            Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-09 09:50 +0200
            Re: Sleeping BUG in khugepaged for i586 Larry Finger <Larry.Finger@lwfinger.net> - 2017-06-09 16:30 +0200
          Re: Sleeping BUG in khugepaged for i586 David Rientjes <rientjes@google.com> - 2017-06-10 00:40 +0200
            Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-10 10:10 +0200
              Re: Sleeping BUG in khugepaged for i586 David Rientjes <rientjes@google.com> - 2017-06-12 01:30 +0200
                Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-12 08:30 +0200
                Re: Sleeping BUG in khugepaged for i586 David Rientjes <rientjes@google.com> - 2017-06-15 02:30 +0200
    Re: Sleeping BUG in khugepaged for i586 David Rientjes <rientjes@google.com> - 2017-06-15 03:20 +0200
      Re: Sleeping BUG in khugepaged for i586 Michal Hocko <mhocko@kernel.org> - 2017-06-15 10:40 +0200
  Re: Sleeping BUG in khugepaged for i586 Larry Finger <Larry.Finger@lwfinger.net> - 2017-06-08 17:30 +0200

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