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Message-ID: <tip-0a7cbf9abe3198461de3d3e97268db32a646ba06@git.kernel.org>
Date: Wed, 13 Aug 2014 03:56:26 -0700
From: tip-bot for Davidlohr Bueso <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
torvalds@...ux-foundation.org, peterz@...radead.org,
rdunlap@...radead.org, jason.low2@...com, tglx@...utronix.de,
davidlohr@...com
Subject: [tip:locking/core] locking/Documentation: Update locking/
mutex-design.txt disadvantages
Commit-ID: 0a7cbf9abe3198461de3d3e97268db32a646ba06
Gitweb: http://git.kernel.org/tip/0a7cbf9abe3198461de3d3e97268db32a646ba06
Author: Davidlohr Bueso <davidlohr@...com>
AuthorDate: Wed, 30 Jul 2014 13:41:56 -0700
Committer: Ingo Molnar <mingo@...nel.org>
CommitDate: Wed, 13 Aug 2014 10:32:04 +0200
locking/Documentation: Update locking/mutex-design.txt disadvantages
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.
Signed-off-by: Davidlohr Bueso <davidlohr@...com>
Acked-by: Jason Low <jason.low2@...com>
Signed-off-by: Peter Zijlstra <peterz@...radead.org>
Cc: aswin@...com
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Randy Dunlap <rdunlap@...radead.org>
Link: http://lkml.kernel.org/r/1406752916-3341-7-git-send-email-davidlohr@hp.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
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
-------------------
--
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