Subject: Re: [PATCH] inet_peer: Optimize inet_getid()

From: Stephen Hemminger <[email-masked]>
Date: Thu, 24 Sep 2009 12:30:20 -0700

On Thu, 24 Sep 2009 21:04:56 +0200
Eric Dumazet <[email-masked]> wrote:

> While investigating for network latencies, I found inet_getid() was a contention point
> for some workloads.
> 
> Fix is straightforward, using cmpxchg() instead of
> a spin_lock_bh()/spin_unlock_bh() pair on a central lock.
> 
> Another possibility was to use an atomic_t and atomic_add_return() but
> the size of struct inet_peer object would had doubled on x86_64 because of
> SLAB_HWCACHE_ALIGN constraint.
> 
> Signed-off-by: Eric Dumazet <[email-masked]>

I thought cmpxchg was not available on all architectures.