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 [thread overview]
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(-)
next reply other threads:[~2016-05-05 20:45 UTC|newest]
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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