From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756288AbcEEUps (ORCPT ); Thu, 5 May 2016 16:45:48 -0400 Received: from www.linutronix.de ([62.245.132.108]:56742 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754952AbcEEUpq (ORCPT ); Thu, 5 May 2016 16:45:46 -0400 Message-Id: <20160505204230.932454245@linutronix.de> User-Agent: quilt/0.63-1 Date: Thu, 05 May 2016 20:44:02 -0000 From: Thomas Gleixner To: LKML Cc: Sebastian Andrzej Siewior , Linus Torvalds , Darren Hart , Peter Zijlstra , Ingo Molnar , Michael Kerrisk , Davidlohr Bueso , Chris Mason , "Carlos O'Donell" , Torvald Riegel , Eric Dumazet Subject: [patch V2 0/7] futex: Add support for process private hashing X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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(-)