Christoph Hellwig a écrit :
> On Thu, Aug 25, 2005 at 11:17:23AM +0200, Eric Dumazet wrote:
> 
>>>But that's not true.  You need to write you own sysctl handler for it,
>>>probably worth adding a generic atomic_t sysctl handler while you're
>>>at it.
>>>
>>
>>I checked linux-2.6.13-rc7 tree, and atomic_read() is just a wrapper to 
>>read v->counter.
> 
> 
> That doesn't matter.  atomic_t is an opaqueue type and you must use the
> atomic_* interfaces to access it.

OK, here is a new clean patch that address this problem (nothing assumed about 
atomics)

This patch removes filp_count_lock spinlock, used to protect files_stat.nr_files.

Introduce an atomic_t atomic_nr_files to keep the exact count, and mirror its 
value into nr_files.

Forcing atomic_nr_files to be in the same cache line than nr_files makes sure 
we dont dirty two cache lines.

There is still a locked memory operation on SMP, but it saves an sti/cli pair.

Thank you

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>