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locking/Documentation: Update locking/mutex-design.txt disadvantages

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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>
This commit is contained in:
Davidlohr Bueso 2014-07-30 13:41:56 -07:00 committed by Ingo Molnar
parent 214e0aed63
commit 0a7cbf9abe
1 changed files with 3 additions and 3 deletions
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6
Documentation/locking/mutex-design.txt
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@ -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
-------------------