netdev - Re: [PATCH] inet_peer: Optimize inet

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Message-ID: <4ABBCF14.5070007@gmail.com>
Date:	Thu, 24 Sep 2009 21:57:08 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] inet_peer: Optimize inet_getid()

Stephen Hemminger a écrit :
> On Thu, 24 Sep 2009 21:04:56 +0200
> Eric Dumazet <eric.dumazet@...il.com> 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 <eric.dumazet@...il.com>
> 
> I thought cmpxchg was not available on all architectures.

Good point Stephen, I forgot about non x86 arches ;)

I'll send an update with cmpxchg() if available, and atomic_t as fallback.
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