From: Darren Hart <dvhart@infradead.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Linus Torvalds <torvalds@linux-foundation.org>,
Darren Hart <darren@dvhart.com>, Ingo Molnar <mingo@kernel.org>,
Michael Kerrisk <mtk.manpages@googlemail.com>,
Davidlohr Bueso <dave@stgolabs.net>, Chris Mason <clm@fb.com>,
"Carlos O'Donell" <carlos@redhat.com>,
Torvald Riegel <triegel@redhat.com>,
Eric Dumazet <edumazet@google.com>
Subject: Re: [patch V2 3/7] futex: Add op for hash preallocation
Date: Thu, 19 May 2016 12:36:42 -0700 [thread overview]
Message-ID: <20160519193642.GA1872@f23x64.localdomain> (raw)
In-Reply-To: <20160519122849.GD3192@twins.programming.kicks-ass.net>
On Thu, May 19, 2016 at 02:28:49PM +0200, Peter Zijlstra wrote:
> On Sat, May 07, 2016 at 10:47:38AM +0200, Thomas Gleixner wrote:
> > On Fri, 6 May 2016, Darren Hart wrote:
>
> > > So this seems like it could be tricky for the user as system libraries, like
> > > glibc, make use of futexes. Can we guarantee that "sys_futex" is not called by
> > > the time main() is called?
> >
> > To the extent of my testing I never observed that the hash was automatically
> > created when I called futex(PREALLOC) right away in main. But yes, that might
> > need some thought.
>
> I suspect that even if glibc uses futexes before main(), they will not
> be contended, because, last time I checked, the C runtime environment is
> very much single threaded unless explicitly made not so by the program.
>
> In any case (re)hashing if the hash is empty is 'easy', if there's already state,
> not so much.
It certainly would be nice to be able to resize the hash if it's empty.
--
Darren Hart
Intel Open Source Technology Center
next prev parent reply other threads:[~2016-05-19 19:36 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-05 20:44 [patch V2 0/7] futex: Add support for process private hashing Thomas Gleixner
2016-05-05 20:44 ` [patch V2 1/7] futex: Add some more function commentry Thomas Gleixner
2016-05-06 17:37 ` Darren Hart
2016-05-05 20:44 ` [patch V2 2/7] futex: Hash private futexes per process Thomas Gleixner
2016-05-06 18:09 ` Darren Hart
2016-05-06 21:56 ` Darren Hart
2016-05-07 8:45 ` Thomas Gleixner
2016-05-11 21:08 ` Darren Hart
2016-05-07 8:44 ` Thomas Gleixner
2016-05-11 21:07 ` Darren Hart
2016-05-27 16:36 ` Sebastian Andrzej Siewior
2016-05-19 12:21 ` Peter Zijlstra
2016-05-27 16:52 ` Sebastian Andrzej Siewior
2016-05-30 8:43 ` Peter Zijlstra
2016-05-19 12:24 ` Peter Zijlstra
2016-05-27 17:10 ` Sebastian Andrzej Siewior
2016-05-30 8:58 ` Peter Zijlstra
2016-05-30 11:08 ` Sebastian Andrzej Siewior
2016-05-30 12:06 ` Peter Zijlstra
2016-05-30 13:37 ` Sebastian Andrzej Siewior
2016-05-30 13:49 ` Peter Zijlstra
2016-05-30 13:59 ` Sebastian Andrzej Siewior
2016-05-30 14:02 ` Peter Zijlstra
2016-05-05 20:44 ` [patch V2 4/7] futex: Add sysctl knobs for process private hash Thomas Gleixner
2016-05-06 18:22 ` Darren Hart
2016-05-27 17:33 ` Sebastian Andrzej Siewior
2016-05-05 20:44 ` [patch V2 3/7] futex: Add op for hash preallocation Thomas Gleixner
2016-05-06 18:18 ` Darren Hart
2016-05-07 8:47 ` Thomas Gleixner
2016-05-07 11:40 ` Thomas Gleixner
2016-05-19 12:28 ` Peter Zijlstra
2016-05-19 19:36 ` Darren Hart [this message]
2016-05-19 12:24 ` Peter Zijlstra
2016-05-19 19:38 ` Darren Hart
2016-05-20 4:50 ` Peter Zijlstra
2016-05-19 12:25 ` Peter Zijlstra
2016-05-27 17:27 ` Sebastian Andrzej Siewior
2016-05-30 8:59 ` Peter Zijlstra
2016-05-05 20:44 ` [patch V2 5/7] perf/bench/futex-hash: Support NUMA Thomas Gleixner
2016-05-05 20:44 ` [patch V2 6/7] perf/bench/futex-hash: Support preallocate hash table Thomas Gleixner
2016-05-05 20:44 ` [patch V2 7/7] futex.2: Document hash preallocation opcode Thomas Gleixner
-- strict thread matches above, loose matches on Subject: below --
2016-05-05 19:03 [patch V2 0/7] Sebastian Andrzej Siewior <bigeasy@linutronix.de>, Linus Torvalds <torvalds@linux-foundation.org>, Darren Hart <darren@dvhart.com>, Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>, Michael Kerrisk <mtk.manpages@googlemail.com>, Davidlohr Bueso <dave@stgolabs.net>, Chris Mason <clm@fb.com>, Carlos O'Donell <carlos@redhat.com>, Torvald Riegel <triegel@redhat.com>, Eric Dumazet <edumazet@google.com> Thomas Gleixner
2016-05-05 19:03 ` [patch V2 3/7] futex: Add op for hash preallocation Thomas Gleixner
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