Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756505AbaGNR2P (ORCPT ); Mon, 14 Jul 2014 13:28:15 -0400 Received: from g4t3427.houston.hp.com ([15.201.208.55]:39891 "EHLO g4t3427.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752433AbaGNR2E (ORCPT ); Mon, 14 Jul 2014 13:28:04 -0400 From: Jason Low To: Peter Zijlstra , Linus Torvalds , "Paul E. McKenney" , Ingo Molnar , Waiman Long , Davidlohr Bueso , linux-kernel@vger.kernel.org Cc: Thomas Gleixner , Rik van Riel , Andrew Morton , "H. Peter Anvin" , Steven Rostedt , Tim Chen , Konrad Rzeszutek Wilk , Aswin Chandramouleeswaran , Scott Norton , Dave Chinner , Jason Low Subject: [PATCH v2 0/5] MCS spinlocks: Cancellable MCS spinlock rework Date: Mon, 14 Jul 2014 10:27:47 -0700 Message-Id: <1405358872-3732-1-git-send-email-jason.low2@hp.com> X-Mailer: git-send-email 1.7.9.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org v1->v2: - Added a patch which uses function + macro for initializing the osq lock as suggested by Steven. - Improved the way we initialize struct rw_semaphore fields with the init macro in patch 5 as suggested by Peter. The main purpose of this patchset is to reduce the size of the cancellable MCS spinlock and reduce the overhead of rwsem (currently the largest lock in the kernel). The overhead of the cancellable MCS lock is a pointer to a per-cpu node structure which requires 64 bits on 64 bit systems. Instead of a pointer to the per-cpu node, we can instead store the CPU # corresponding to the node in atomic_t. This reduces the overhead by 32 bits on 64 bit systems. This then opens the opportunity to reduce the size of the rw_semaphore structure (one of the current users of this MCS lock) by moving around some of its fields. Due to padding, we would reduce the size of that structure by 64 bits (on 64 bit systems). This makes it more in line with the size of the mutex structure. Jason Low (5): MCS spinlocks: Rename optimistic_spin_queue to optimistic_spin_node MCS spinlocks: Convert osq lock to atomic_t to reduce overhead MCS spinlocks: Introduce and use init macro and function for osq locks MCS spinlocks: Micro-optimize osq_unlock() rwsem: Reduce the size of struct rw_semaphore include/linux/mutex.h | 4 +- include/linux/osq_lock.h | 27 +++++++++++++++++ include/linux/rwsem.h | 28 +++++++---------- kernel/locking/mcs_spinlock.c | 64 ++++++++++++++++++++++++++++++---------- kernel/locking/mcs_spinlock.h | 9 +++-- kernel/locking/mutex.c | 2 +- kernel/locking/rwsem-xadd.c | 2 +- 7 files changed, 96 insertions(+), 40 deletions(-) create mode 100644 include/linux/osq_lock.h -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/