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From: David Miller <davem@davemloft.net>
Subject: Re: [PATCH] inet_peer: Optimize inet_getid()
Date: Mon, 05 Oct 2009 00:08:18 -0700 (PDT)
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From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 24 Sep 2009 22:44:53 +0200

> [PATCH] inet_peer: Optimize inet_getid()
> 
> While investigating for network latencies, I found inet_getid() was a contention point
> for some workloads.
> 
> If __HAVE_ARCH_CMPXCHG is defined, we can use cmpxchg() instead of
> a spin_lock_bh()/spin_unlock_bh() pair on a central lock.
> 
> On other arches, we can use an atomic_t instead of a u16,
> and atomic_add_return(). This might grow memory usage a bit, unless
> someone invents atomic16_t :)
> 
> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

I can't apply this, it's going to break the build on some
architectures.

For example, sparc64 only supports cmpxchg on u32 and u64
objects, but you're trying to use it on a u16 here.