> What kinds of operations are protected by read locks?

Looking at almost any of the global data structures, such as error tables, OID 
tables, and so on.

>Often, RW locks aren't a win because maintaining just the read locks (without 
>any writers) introduces contention at the hardware level, and parallelism does 
>not increase all that much as a result.  Paul McKenney's dissertation on RCU 
>has some examples.

We've monitored one of our applications, an SSL-terminating HTTP proxy server, 
under load. Of all the mutexes (futex, actually) in the system, the "error" 
lock is the most highly contended one.  I'll see about posting some statistics.

        /r$

--  
Principal Security Engineer
Akamai Technologies, Cambridge, MA
IM: rs...@jabber.me; Twitter: RichSalz
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