Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751359AbaGGTA6 (ORCPT ); Mon, 7 Jul 2014 15:00:58 -0400 Received: from g2t1383g.austin.hp.com ([15.217.136.92]:3289 "EHLO g2t1383g.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750868AbaGGTA4 (ORCPT ); Mon, 7 Jul 2014 15:00:56 -0400 From: Jason Low To: peterz@infradead.org, torvalds@linux-foundation.org, paulmck@linux.vnet.ibm.com, mingo@kernel.org, Waiman.Long@hp.com, davidlohr@hp.com, linux-kernel@vger.kernel.org Cc: tglx@linutronix.de, riel@redhat.com, rostedt@goodmis.org, akpm@linux-foundation.org, hpa@zytor.com, tim.c.chen@linux.intel.com, konrad.wilk@oracle.com, aswin@hp.com, scott.norton@hp.com, chegu_vinod@hp.com, jason.low2@hp.com Subject: [PATCH 4/4] rwsem: Reduce the size of struct rw_semaphore Date: Mon, 7 Jul 2014 11:50:19 -0700 Message-Id: <1404759019-4268-5-git-send-email-jason.low2@hp.com> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1404759019-4268-1-git-send-email-jason.low2@hp.com> References: <1404759019-4268-1-git-send-email-jason.low2@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Recent optimistic spinning additions to rwsem provide significant performance benefits on many workloads on large machines. The cost of it was increasing the size of the rwsem structure by up to 128 bits. However, now that the previous patches in this series bring the overhead of struct optimistic_spin_queue to 32 bits, this patch reorders some fields in struct rw_semaphore such that we can reduce the overhead of the rwsem structure by 64 bits (on 64 bit systems). The extra overhead required for rwsem optimistic spinning would now be up to 8 additional bytes instead of up to 16 bytes. Additionally, the size of rwsem would now be more in line with mutexes. Signed-off-by: Jason Low --- include/linux/rwsem.h | 8 ++++---- 1 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 9fdcdd0..f6c54c0 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -24,15 +24,15 @@ struct rw_semaphore; /* All arch specific implementations share the same struct */ struct rw_semaphore { long count; - raw_spinlock_t wait_lock; struct list_head wait_list; + raw_spinlock_t wait_lock; #ifdef CONFIG_SMP + struct optimistic_spin_queue osq; /* spinner MCS lock */ /* * Write owner. Used as a speculative check to see * if the owner is running on the cpu. */ struct task_struct *owner; - struct optimistic_spin_queue osq; /* spinner MCS lock */ #endif #ifdef CONFIG_DEBUG_LOCK_ALLOC struct lockdep_map dep_map; @@ -66,10 +66,10 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) #if defined(CONFIG_SMP) && !defined(CONFIG_RWSEM_GENERIC_SPINLOCK) #define __RWSEM_INITIALIZER(name) \ { RWSEM_UNLOCKED_VALUE, \ - __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock), \ LIST_HEAD_INIT((name).wait_list), \ + __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock), \ + { ATOMIC_INIT(OSQ_UNLOCKED_VAL) }, /* osq */ \ NULL, /* owner */ \ - { ATOMIC_INIT(OSQ_UNLOCKED_VAL) } /* osq */ \ __RWSEM_DEP_MAP_INIT(name) } #else #define __RWSEM_INITIALIZER(name) \ -- 1.7.1 -- 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/