Re: [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier
Date	2016-09-09 09:50 +0200
Message-ID	<sfoJs-8tz-19@gated-at.bofh.it> (permalink)
References	(4 earlier) <saUTD-2k2-7@gated-at.bofh.it> <scgIp-4Kp-1@gated-at.bofh.it> <sf1tw-2mB-41@gated-at.bofh.it> <sfhHX-4i4-1@gated-at.bofh.it> <sflVf-6P8-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Sep 08, 2016 at 09:39:45PM -0700, Andy Lutomirski wrote:
> If they're busy threads, shouldn't the yield return immediately
> because the threads are still ready to run?  Lazy TLB won't do much
> unless you get the kernel in some state where it's running in the
> context of a different kernel thread and hasn't switched to
> swapper_pg_dir.  IIRC idle works like that, but you'd need to actually
> sleep to go idle.

Right, a task doing:

	for (;;) sched_yield();

esp. when its the only runnable thread on the CPU, is a busy thread. It
will not enter switch_mm(), which was where the invalidate hook was
placed IIRC.

Thread

[PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-25 21:10 +0200
  Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-25 22:00 +0200
  [PATCH RFC v2] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-25 22:20 +0200
  [PATCH RFC v3] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-25 23:10 +0200
    Re: [PATCH RFC v3] x86,mm,sched: make lazy TLB mode even lazier Ingo Molnar <mingo@kernel.org> - 2016-08-27 10:10 +0200
      Re: [PATCH RFC v3] x86,mm,sched: make lazy TLB mode even lazier Linus Torvalds <torvalds@linux-foundation.org> - 2016-08-28 01:10 +0200
        [PATCH RFC v4] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-30 22:00 +0200
          [PATCH RFC v5] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-30 23:10 +0200
        [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-31 18:40 +0200
          Re: [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier Ingo Molnar <mingo@kernel.org> - 2016-09-08 09:00 +0200
            Re: [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier Benjamin Serebrin <serebrin@google.com> - 2016-09-09 02:20 +0200
              Re: [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier Andy Lutomirski <luto@amacapital.net> - 2016-09-09 06:50 +0200
                Re: [PATCH RFC v6] x86,mm,sched: make lazy TLB mode even lazier Peter Zijlstra <peterz@infradead.org> - 2016-09-09 09:50 +0200
      Re: [PATCH RFC v3] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-29 17:30 +0200
  Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier "H. Peter Anvin" <hpa@zytor.com> - 2016-08-26 00:50 +0200
    Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-29 18:10 +0200
  Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Andy Lutomirski <luto@amacapital.net> - 2016-08-28 10:20 +0200
    Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Rik van Riel <riel@redhat.com> - 2016-08-29 17:10 +0200
      Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Andy Lutomirski <luto@amacapital.net> - 2016-08-30 02:00 +0200
        Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier "H. Peter Anvin" <hpa@zytor.com> - 2016-08-30 03:20 +0200
          Re: [PATCH RFC UGLY] x86,mm,sched: make lazy TLB mode even lazier Andy Lutomirski <luto@amacapital.net> - 2016-08-30 20:30 +0200

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