netdev - Re: [PATCH] inetpeer: optimizations

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Date:	Sat, 05 Dec 2009 22:29:49 +0100
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH] inetpeer: optimizations

Eric Dumazet wrote, On 12/05/2009 01:11 PM:

> - Use atomic_dec_and_test() in inet_putpeer()

atomic_dec_and_lock()?

>   This takes/dirties the lock only if necessary.
...

>  void inet_putpeer(struct inet_peer *p)
>  {
> -	spin_lock_bh(&inet_peer_unused_lock);
> -	if (atomic_dec_and_test(&p->refcnt)) {
> -		list_add_tail(&p->unused, &unused_peers);
> +	local_bh_disable();
> +	if (atomic_dec_and_lock(&p->refcnt, &unused_peers.lock)) {

Why not:
	if (atomic_dec_and_test(&p->refcnt)) {
		spin_lock_bh(&inet_peer_unused_lock);
		...
Jarek P.
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