From: Thomas Gleixner <tglx@linutronix.de>
To: LKML <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Darren Hart <darren@dvhart.com>,
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 0/7] futex: Add support for process private hashing
Date: Thu, 28 Apr 2016 16:42:06 -0000 [thread overview]
Message-ID: <20160428161742.363543816@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 series comes with a new 'stupid' hash function based on the good old
modulu prime. That function provides way better hash results than
hash_ptr/hash_long() for small hash sizes.
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.
Results from our testing in nice colored charts are available here:
perf bench futex-hash run parallel on 4 nodes with global hash and various
sized private hashes and various numbers of futexes per thread
https://tglx.de/~tglx/f-ops.png
perf bench futex-hash run parallel on 4 nodes with global hash and various
sized private hashes using the new hash_mod() and various numbers of futexes
per thread
https://tglx.de/~tglx/f-ops.png
perf bench futex-hash run parallel on 4 nodes with global hash and various
sized private hashes using hash_long() and various numbers of futexes per
thread
https://tglx.de/~tglx/f-ops-hlong.png
perf bench futex-hash run parallel on 2 nodes with global hash and various
sized private hashes and various numbers of futexes per thread
https://tglx.de/~tglx/f-ops-2.png
perf bench futex-hash run parallel on 4 nodes with global hash and various
sized private hashes using hash_mod(). 1 futex per thread and various thread
numbers.
https://tglx.de/~tglx/f-ops-mod-t.png
perf bench futex-hash run parallel on 4 nodes with global hash and various
sized private hashes using hash_long(). 1 futex per thread and various thread
numbers.
https://tglx.de/~tglx/f-ops-hlong-t.png
Thanks,
tglx
----
Documentation/sysctl/kernel.txt | 17 +++
b/include/linux/futex_types.h | 14 ++
b/lib/hashmod.c | 44 ++++++++
include/linux/futex.h | 39 +++++--
include/linux/hash.h | 28 +++++
include/linux/mm_types.h | 4
include/uapi/linux/futex.h | 1
init/Kconfig | 5
kernel/fork.c | 3
kernel/futex.c | 219 +++++++++++++++++++++++++++++++++++++++-
kernel/sysctl.c | 21 +++
lib/Kconfig | 3
lib/Makefile | 1
tools/perf/bench/Build | 4
tools/perf/bench/futex-hash.c | 101 ++++++++++++++++--
tools/perf/bench/futex.h | 5
16 files changed, 486 insertions(+), 23 deletions(-)
next reply other threads:[~2016-04-28 16:44 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-28 16:42 Thomas Gleixner [this message]
2016-04-28 16:42 ` [patch 1/7] futex: Add some more function commentry Thomas Gleixner
2016-04-28 16:42 ` [patch 2/7] lib/hashmod: Add modulo based hash mechanism Thomas Gleixner
2016-04-28 18:32 ` Linus Torvalds
2016-04-28 23:26 ` Thomas Gleixner
2016-04-29 2:25 ` Linus Torvalds
2016-04-30 13:02 ` Thomas Gleixner
2016-04-30 16:45 ` Eric Dumazet
2016-04-30 17:12 ` Linus Torvalds
2016-04-30 17:37 ` Eric Dumazet
2016-06-12 12:18 ` Sandy Harris
2016-04-29 21:10 ` Linus Torvalds
2016-04-29 23:51 ` Linus Torvalds
2016-04-30 1:34 ` Rik van Riel
2016-05-02 9:39 ` Torvald Riegel
2016-04-30 15:22 ` Thomas Gleixner
2016-04-28 16:42 ` [patch 3/7] futex: Hash private futexes per process Thomas Gleixner
2016-04-28 16:42 ` [patch 4/7] futex: Add op for hash preallocation Thomas Gleixner
2016-04-28 16:42 ` [patch 5/7] futex: Add sysctl knobs for process private hash Thomas Gleixner
2016-04-28 16:42 ` [patch 6/7] perf/bench/futex-hash: Support NUMA Thomas Gleixner
2016-04-28 16:42 ` [patch 7/7] perf/bench/futex-hash: Support preallocate hash table Thomas Gleixner
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