Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755898AbaG3Umd (ORCPT ); Wed, 30 Jul 2014 16:42:33 -0400 Received: from g2t2353.austin.hp.com ([15.217.128.52]:41484 "EHLO g2t2353.austin.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751761AbaG3UmM (ORCPT ); Wed, 30 Jul 2014 16:42:12 -0400 From: Davidlohr Bueso To: peterz@infradead.org, mingo@kernel.org Cc: jason.low2@hp.com, davidlohr@hp.com, aswin@hp.com, linux-kernel@vger.kernel.org Subject: [PATCH -tip v2 7/7] Documentation: Update locking/mutex-design.txt disadvantages Date: Wed, 30 Jul 2014 13:41:56 -0700 Message-Id: <1406752916-3341-7-git-send-email-davidlohr@hp.com> X-Mailer: git-send-email 1.8.1.4 In-Reply-To: <1406752916-3341-1-git-send-email-davidlohr@hp.com> References: <1406752916-3341-1-git-send-email-davidlohr@hp.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Fortunately Jason was able to reduce some of the overhead we had introduced in the original rwsem optimistic spinning - an it is now the same size as mutexes. Update the documentation accordingly. Acked-by: Jason Low Signed-off-by: Davidlohr Bueso --- Documentation/locking/mutex-design.txt | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/Documentation/locking/mutex-design.txt b/Documentation/locking/mutex-design.txt index ee231ed..60c482d 100644 --- a/Documentation/locking/mutex-design.txt +++ b/Documentation/locking/mutex-design.txt @@ -145,9 +145,9 @@ Disadvantages Unlike its original design and purpose, 'struct mutex' is larger than most locks in the kernel. E.g: on x86-64 it is 40 bytes, almost twice -as large as 'struct semaphore' (24 bytes) and 8 bytes shy of the -'struct rw_semaphore' variant. Larger structure sizes mean more CPU -cache and memory footprint. +as large as 'struct semaphore' (24 bytes) and tied, along with rwsems, +for the largest lock in the kernel. Larger structure sizes mean more +CPU cache and memory footprint. When to use mutexes ------------------- -- 1.8.1.4 -- 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/