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[patch V2 0/7] futex: Add support for process private hashing

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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(-)

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[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
  [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
  [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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