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Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf

From Rik van Riel <riel@redhat.com>
Newsgroups linux.kernel
Subject Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf
Date 2017-09-11 03:20 +0200
Message-ID <uolyi-3QJ-13@gated-at.bofh.it> (permalink)
References (7 earlier) <unSFY-IW-21@gated-at.bofh.it> <unSPE-Nx-5@gated-at.bofh.it> <unSZj-R2-7@gated-at.bofh.it> <unTsm-1hK-31@gated-at.bofh.it> <unTC1-1le-3@gated-at.bofh.it>
Organization Red Hat, Inc

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On Sat, 2017-09-09 at 12:28 -0700, Andy Lutomirski wrote:
> -
> I propose the following fix.  If PCID is on, then, in
> enter_lazy_tlb(), we switch to init_mm with the no-flush flag set.
> (And we give init_mm its own dedicated ASID to keep it simple and
> fast
> -- no need to use the LRU ASID mapping to assign one
> dynamically.)  We
> clear the bit in mm_cpumask.  That is, we more or less just skip the
> whole lazy TLB optimization and rely on PCID CPUs having reasonably
> fast CR3 writes.  No extra IPIs.

Avoiding the IPIs is probably what matters the most, especially
on systems with deep C states, and virtual machines where the
host may be running something else, causing the IPI service time
to go through the roof for idle VCPUs.

> Also, sorry Rik, this means your old increased laziness optimization
> is dead in the water.  It will have exactly the same speculative load
> problem.

Doesn't a memory barrier solve that speculative load
problem?

The memory barrier could be added only to the path
that potentially skips reloading the TLB, under the
assumption that a memory barrier is cheaper than a
TLB reload (even with ASID).

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Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-05 09:40 +0200
  Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Peter Zijlstra <peterz@infradead.org> - 2017-09-05 11:00 +0200
    Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-05 12:00 +0200
      Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Thomas Gleixner <tglx@linutronix.de> - 2017-09-06 15:00 +0200
        Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-06 15:20 +0200
          Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-07 08:30 +0200
            Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Thomas Gleixner <tglx@linutronix.de> - 2017-09-08 08:30 +0200
              Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-08 10:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-08 11:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 11:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Ingo Molnar <mingo@kernel.org> - 2017-09-08 12:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 12:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 13:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-08 18:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-08 19:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-08 23:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 00:00 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 01:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 01:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 02:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 03:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@amacapital.net> - 2017-09-09 03:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 20:00 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 20:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 08:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 12:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 13:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 15:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 15:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 15:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 16:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 16:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 16:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 16:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 18:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 19:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 19:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 19:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 20:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 20:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 20:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 20:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 20:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 20:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-09 21:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-09 21:40 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-10 06:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@amacapital.net> - 2017-09-10 22:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Peter Zijlstra <peterz@infradead.org> - 2017-09-10 22:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Ingo Molnar <mingo@kernel.org> - 2017-09-17 19:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building  e.g. perf Rik van Riel <riel@redhat.com> - 2017-09-11 03:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Andy Lutomirski <luto@kernel.org> - 2017-09-11 03:50 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building  e.g. perf Rik van Riel <riel@redhat.com> - 2017-09-11 17:10 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g. perf Linus Torvalds <torvalds@linux-foundation.org> - 2017-09-09 21:30 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-12 09:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Markus Trippelsdorf <markus@trippelsdorf.de> - 2017-09-09 10:20 +0200
                Re: Current mainline git (24e700e291d52bd2) hangs when building e.g.  perf Borislav Petkov <bp@alien8.de> - 2017-09-08 17:00 +0200

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