Messages in this thread | | | Subject | Re: [PATCH -tip/master 7/7] Documentation: Update locking/mutex-design.txt disadvantages | From | Jason Low <> | Date | Mon, 28 Jul 2014 11:09:27 -0700 |
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On Sun, 2014-07-27 at 22:18 -0700, Davidlohr Bueso wrote: > 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> > --- > 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,
My suggestion here is for the above to say 'struct rw_semaphore' instead of rwsems.
Acked-by: Jason Low <jason.low2@hp.com>
> +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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