Re: 2.4.23aa2 (bugfixes and important VM improvements for the high end)

[Andrea Arcangeli]

On Fri, Mar 05, 2004 at 08:19:55PM +0000, Jamie Lokier wrote:
> Andrew Morton wrote:
> >   We believe that this could cause misbehaviour of such things as the
> >   boehm garbage collector.  This patch provides the mprotect() atomicity by
> >   performing all userspace copies under page_table_lock.
> 
> Can you use a read-write lock, so that userspace copies only need to
> take the lock for reading?  That doesn't eliminate cacheline bouncing
> but does eliminate the serialisation.

normally the bouncing would be the only overhead, but here I also think
the serialization is a significant factor of the contention because the
critical section is taking lots of time. So I would expect some
improvement by using a read/write lock.
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