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From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: 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>
Subject: [patch V2 0/7] futex: Add support for process private hashing
Date: Thu, 05 May 2016 20:44:02 -0000
Message-ID: <20160505204230.932454245@linutronix.de> (raw)

The standard futex mechanism in the Linux kernel uses a global hash to store
transient state. Collisions on that hash can lead to performance degradation
and on real-time enabled kernels to unbound priority inversions.

This new attempt to solve the issue does not require user space changes and
operates transparently. On the first futex operation of a process the kernel
allocates a hash private to the process. All process private futexes are
hashed in this hash. Process shared futexes still use the global hash.

For RT applications and pathological use cases a new futex op is provided
which allows the application to preallocate and thereby size the process
private hash.

The last two patches add support to the perf futex-hash benchmark so test can
be run on nodes and the preallocation sizing can be tested.

The last patch contains a first update for the futex man page.

The difference vs. V1 of this series is that it uses hash_long() now that the
hash_64 implementation has been fixed in mainline. The performance numbers are
more or less the same as with V1 [1].

Thanks,

	tglx

[1] http://lkml.kernel.org/r/20160428161742.363543816@linutronix.de

----
 Documentation/sysctl/kernel.txt |   17 +++
 b/include/linux/futex_types.h   |   12 ++
 include/linux/futex.h           |   39 +++++--
 include/linux/mm_types.h        |    4 
 include/uapi/linux/futex.h      |    1 
 init/Kconfig                    |    4 
 kernel/fork.c                   |    3 
 kernel/futex.c                  |  215 +++++++++++++++++++++++++++++++++++++++-
 kernel/sysctl.c                 |   21 +++
 tools/perf/bench/Build          |    4 
 tools/perf/bench/futex-hash.c   |  101 ++++++++++++++++--
 tools/perf/bench/futex.h        |    5 
 12 files changed, 403 insertions(+), 23 deletions(-)

             reply index

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-05 20:44 Thomas Gleixner [this message]
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
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

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