Re: [patch V2 2/7] futex: Hash private futexes per process

From	Darren Hart <dvhart@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [patch V2 2/7] futex: Hash private futexes per process
Date	2016-05-11 23:10 +0200
Message-ID	<rxJyi-84d-13@gated-at.bofh.it> (permalink)
References	<rvynE-79b-3@gated-at.bofh.it> <rvynF-79b-21@gated-at.bofh.it> <rvSmn-1A4-29@gated-at.bofh.it> <rvVWV-4tS-1@gated-at.bofh.it> <rw65X-6Am-1@gated-at.bofh.it>
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On Sat, May 07, 2016 at 10:45:57AM +0200, Thomas Gleixner wrote:
> On Fri, 6 May 2016, Darren Hart wrote:
>  > It would be good to have a way to detect that the process private hash table was
> > > successfully created. Perhaps a /proc/pid/ feature? This would allow us to write
> > > a functional futex test for tools/testing/selftests/futex
> > 
> > I suppose we could just use FUTEX_PREALLOC_HASH for this purpose, passing in the
> > default hash size. This will either return the default, the previously set
> > value, or 0, indicating the global hash is being used. That should be sufficient
> > for programatically determining the state of the system.
> 
> Right.
>  
> > The /proc/pid/futex_hash_size option may still be convenient for other purposes.
> > Perhaps with a -1 indicating it hasn't been set yet.
> 
> Dunno, whether that's valuable, but it can be done on top.

Agreed. We can leave that to the kselftest patch, and if it's easily done
without this, then we're done. If not, we can look at it then.

-- 
Darren Hart
Intel Open Source Technology Center

Thread

[patch V2 0/7] futex: Add support for process private hashing Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200
  [patch V2 4/7] futex: Add sysctl knobs for process private hash Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200
    Re: [patch V2 4/7] futex: Add sysctl knobs for process private hash Darren Hart <dvhart@infradead.org> - 2016-05-06 20:30 +0200
      Re: [patch V2 4/7] futex: Add sysctl knobs for process private hash Sebastian Andrzej Siewior <sebastian@breakpoint.cc> - 2016-05-27 19:40 +0200
  [patch V2 5/7] perf/bench/futex-hash: Support NUMA Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200
  [patch V2 2/7] futex: Hash private futexes per process Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200
    Re: [patch V2 2/7] futex: Hash private futexes per process Darren Hart <dvhart@infradead.org> - 2016-05-06 20:10 +0200
      Re: [patch V2 2/7] futex: Hash private futexes per process Darren Hart <dvhart@infradead.org> - 2016-05-07 00:00 +0200
        Re: [patch V2 2/7] futex: Hash private futexes per process Thomas Gleixner <tglx@linutronix.de> - 2016-05-07 10:50 +0200
          Re: [patch V2 2/7] futex: Hash private futexes per process Darren Hart <dvhart@infradead.org> - 2016-05-11 23:10 +0200
      Re: [patch V2 2/7] futex: Hash private futexes per process Thomas Gleixner <tglx@linutronix.de> - 2016-05-07 10:50 +0200
        Re: [patch V2 2/7] futex: Hash private futexes per process Darren Hart <dvhart@infradead.org> - 2016-05-11 23:10 +0200
        Re: [patch V2 2/7] futex: Hash private futexes per process Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-05-27 18:40 +0200
    Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-19 14:30 +0200
      Re: [patch V2 2/7] futex: Hash private futexes per process Sebastian Andrzej Siewior <sebastian@breakpoint.cc> - 2016-05-27 19:00 +0200
        Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-30 10:50 +0200
    Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-19 14:30 +0200
      Re: [patch V2 2/7] futex: Hash private futexes per process Sebastian Andrzej Siewior <sebastian@breakpoint.cc> - 2016-05-27 19:20 +0200
        Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-30 11:00 +0200
          Re: [patch V2 2/7] futex: Hash private futexes per process Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-05-30 13:10 +0200
            Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-30 14:10 +0200
              Re: [patch V2 2/7] futex: Hash private futexes per process Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-05-30 15:40 +0200
                Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-30 15:50 +0200
                Re: [patch V2 2/7] futex: Hash private futexes per process Peter Zijlstra <peterz@infradead.org> - 2016-05-30 16:10 +0200
                Re: [patch V2 2/7] futex: Hash private futexes per process Sebastian Andrzej Siewior <bigeasy@linutronix.de> - 2016-05-30 16:10 +0200
  [patch V2 6/7] perf/bench/futex-hash: Support preallocate hash table Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200
  [patch V2 1/7] futex: Add some more function commentry Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200
    Re: [patch V2 1/7] futex: Add some more function commentry Darren Hart <dvhart@infradead.org> - 2016-05-06 19:40 +0200
  [patch V2 7/7] futex.2: Document hash preallocation opcode Thomas Gleixner <tglx@linutronix.de> - 2016-05-05 22:50 +0200

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