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>Per-CPU Data</H1
><P
> A great technique for avoiding locking which is used fairly
widely is to duplicate information for each CPU. For example,
if you wanted to keep a count of a common condition, you could
use a spin lock and a single counter. Nice and simple.
</P
><P
> If that was too slow [it's probably not], you could instead
use a counter for each CPU [don't], then none of them need an
exclusive lock [you're wasting your time here]. To make sure
the CPUs don't have to synchronize caches all the time, align
the counters to cache boundaries by appending
`__cacheline_aligned' to the declaration
(<TT
CLASS="FILENAME"
>include/linux/cache.h</TT
>).
[Can't you think of anything better to do?]
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> They will need a read lock to access their own counters,
however. That way you can use a write lock to grant exclusive
access to all of them at once, to tally them up.
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