Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754032Ab3HFDNI (ORCPT ); Mon, 5 Aug 2013 23:13:08 -0400 Received: from g1t0027.austin.hp.com ([15.216.28.34]:45846 "EHLO g1t0027.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753678Ab3HFDNG (ORCPT ); Mon, 5 Aug 2013 23:13:06 -0400 From: Waiman Long Cc: Waiman Long , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Steven Rostedt , Linus Torvalds , Benjamin Herrenschmidt , Andi Kleen , "Chandramouleeswaran, Aswin" , "Norton, Scott J" Subject: [PATCH v7 0/4] Lockless update of reference count protected by spinlock Date: Mon, 5 Aug 2013 23:12:35 -0400 Message-Id: <1375758759-29629-1-git-send-email-Waiman.Long@hp.com> X-Mailer: git-send-email 1.7.1 To: Alexander Viro , Jeff Layton , Miklos Szeredi , Ingo Molnar , Thomas Gleixner Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4068 Lines: 91 v6->v7: - Substantially reduce the number of patches from 14 to 4 because a lot of the minor filesystem related changes had been merged to v3.11-rc1. - Remove architecture specific customization (LOCKREF_WAIT_SHIFT & LOCKREF_RETRY_COUNT). - Tune single-thread performance of lockref_put/get to within 10% of old lock->update->unlock code. v5->v6: - Add a new GENERIC_SPINLOCK_REFCOUNT config parameter for using the generic implementation. - Add two parameters LOCKREF_WAIT_SHIFT and LOCKREF_RETRY_COUNT which can be specified differently for each architecture. - Update various spinlock_refcount.* files to incorporate review comments. - Replace reference of d_refcount() macro in Lustre filesystem code in the staging tree to use the new d_count() helper function. v4->v5: - Add a d_count() helper for readonly access of reference count and change all references to d_count outside of dcache.c, dcache.h and namei.c to use d_count(). v3->v4: - Replace helper function access to d_lock and d_count by using macros to redefine the old d_lock name to the spinlock and new d_refcount name to the reference count. This greatly reduces the size of this patchset from 25 to 12 and make it easier to review. v2->v3: - Completely revamp the packaging by adding a new lockref data structure that combines the spinlock with the reference count. Helper functions are also added to manipulate the new data structure. That results in modifying over 50 files, but the changes were trivial in most of them. - Change initial spinlock wait to use a timeout. - Force 64-bit alignment of the spinlock & reference count structure. - Add a new way to use the combo by using a new union and helper functions. v1->v2: - Add one more layer of indirection to LOCK_WITH_REFCOUNT macro. - Add __LINUX_SPINLOCK_REFCOUNT_H protection to spinlock_refcount.h. - Add some generic get/put macros into spinlock_refcount.h. This patchset supports a generic mechanism to atomically update a reference count that is protected by a spinlock without actually acquiring the lock itself. If the update doesn't succeeed, the caller will have to acquire the lock and update the reference count in the the old way. This will help in situation where there is a lot of spinlock contention because of frequent reference count update. The d_lock and d_count fields of the struct dentry in dcache.h was modified to use the new lockref data structure and the d_lock name is now a macro to the actual spinlock. This patch set causes significant performance improvement in the short workload of the AIM7 benchmark on a 8-socket x86-64 machine with 80 cores. Thank to Thomas Gleixner, Andi Kleen and Linus for their valuable input in shaping this patchset. Signed-off-by: Waiman Long Waiman Long (4): spinlock: A new lockref structure for lockless update of refcount spinlock: Enable x86 architecture to do lockless refcount update dcache: replace d_lock/d_count by d_lockcnt dcache: Enable lockless update of dentry's refcount arch/x86/Kconfig | 3 + fs/dcache.c | 78 +++++++------ fs/namei.c | 6 +- include/asm-generic/spinlock_refcount.h | 46 +++++++ include/linux/dcache.h | 22 ++-- include/linux/spinlock_refcount.h | 126 ++++++++++++++++++++ kernel/Kconfig.locks | 15 +++ lib/Makefile | 2 + lib/spinlock_refcount.c | 198 +++++++++++++++++++++++++++++++ 9 files changed, 449 insertions(+), 47 deletions(-) create mode 100644 include/asm-generic/spinlock_refcount.h create mode 100644 include/linux/spinlock_refcount.h create mode 100644 lib/spinlock_refcount.c -- 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/