Re: [PATCH 1/19] MUTEX: Introduce simple mutex implementation

[Jesse Barnes]

On Friday, December 16, 2005 2:53 pm, David S. Miller wrote:
> When the write comes along, the next transaction occurs to kick it
> out the other cpu(s) caches and then the local line is placed into
> Owned state.
>
> I'll have to add "put write prefetch in CAS sequences" onto my sparc64
> TODO list :-)

Note that under contention prefetching with a write bias can cause a lot 
more cache line bouncing than a regular load into shared state (assuming 
you do a load and test before you try the CAS).  We actually saw this on 
large Altix machines, 
http://lia64.bkbits.net:8080/to-linus-2.5/cset%403f2082b3xCvMG9OSeNu3aWhoe6jnOg?nav=index.html|
src/.|src/include|src/include/asm-ia64|
related/include/asm-ia64/spinlock.h fixed things up for us.

Jesse
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