Commit 0a7cbf9a authored Jul 30, 2014 by Davidlohr Bueso Committed by Ingo Molnar Aug 13, 2014

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@hp.com>
Acked-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: aswin@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Link: http://lkml.kernel.org/r/1406752916-3341-7-git-send-email-davidlohr@hp.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 214e0aed

Documentation/locking/mutex-design.txt

+3 −3

Original line number	Diff line number	Diff line
		@@ -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
		-------------------