From: Davidlohr Bueso Date: Wed, 30 Jul 2014 20:41:56 +0000 (-0700) Subject: locking/Documentation: Update locking/mutex-design.txt disadvantages X-Git-Tag: v3.18-rc1~72^2~9 X-Git-Url: https://git.kernelconcepts.de/?p=karo-tx-linux.git;a=commitdiff_plain;h=0a7cbf9abe3198461de3d3e97268db32a646ba06 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 Acked-by: Jason Low Signed-off-by: Peter Zijlstra Cc: aswin@hp.com Cc: Linus Torvalds Cc: Randy Dunlap Link: http://lkml.kernel.org/r/1406752916-3341-7-git-send-email-davidlohr@hp.com Signed-off-by: Ingo Molnar --- diff --git a/Documentation/locking/mutex-design.txt b/Documentation/locking/mutex-design.txt index ee231ed09ec6..60c482df1a38 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 -------------------