Re: 2.5.69-mm1

[Dipankar Sarma <dipankar@in.ibm.com>]

On Tue, May 06, 2003 at 05:02:22AM -0700, David S. Miller wrote:
> On Tue, 2003-05-06 at 04:09, Dipankar Sarma wrote:
> > That brings me to the point - with the fget-speedup patch, we should
> > probably change ->file_lock back to an rwlock again. We now take this
> > lock only when fd table is shared and under such situation the rwlock
> > should help. Andrew, it that ok ?
> 
> rwlocks believe it or not tend not to be superior over spinlocks,
> they actually promote cache line thrashing in the case they
> are actually being effective (>1 parallel reader)

Provided there isn't a very heavy contention among readers for the spin_lock.
There is no evidence that this happens with ->file_lock as
spin_lock, so I guess we are ok for now. We should probably watch out
for some multi-threaded programs (Java->posix-threads ?) on
large smp boxes though.

Thanks
Dipankar