From: David Miller <davem@davemloft.net>
To: dada1@cosmosbay.com
Cc: andi@firstfloor.org, netdev@vger.kernel.org
Subject: Re: [PATCH] net: release skb->dst in sock_queue_rcv_skb()
Date: Tue, 25 Nov 2008 18:04:04 -0800 (PST) [thread overview]
Message-ID: <20081125.180404.157859705.davem@davemloft.net> (raw)
In-Reply-To: <492C919E.3050108@cosmosbay.com>
From: Eric Dumazet <dada1@cosmosbay.com>
Date: Wed, 26 Nov 2008 01:00:30 +0100
> In the meantime, what do you think of the following patch ?
>
> [PATCH] net: release skb->dst in sock_queue_rcv_skb()
>
> When queuing a skb to sk->sk_receive_queue, we can release its dst, not
> anymore needed.
> Since current cpu did the dst_hold(), refcount is probably still hot
> int this cpu caches.
>
> This avoids readers to access the original dst to decrement its refcount,
> possibly a long time after packet reception. This should speedup UDP
> and RAW receive path.
>
> Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
I guess the idea is that if we release quickly we'll not have
to reget the cacheline in owned state.
I wonder if this might actually slightly hurt loads like tbench where
we are banging on the refcnt constantly on every cpu anyways.
Can you do a quick check?
next prev parent reply other threads:[~2008-11-26 2:04 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-11-24 8:57 [RFC] Could we avoid touching dst->refcount in some cases ? Eric Dumazet
2008-11-24 9:42 ` Andi Kleen
2008-11-24 10:14 ` Eric Dumazet
2008-11-24 11:24 ` [PATCH] net: avoid a pair of dst_hold()/dst_release() in ip_append_data() Eric Dumazet
2008-11-24 13:59 ` [PATCH] net: avoid a pair of dst_hold()/dst_release() in ip_push_pending_frames() Eric Dumazet
2008-11-25 0:07 ` David Miller
2008-11-24 23:55 ` [PATCH] net: avoid a pair of dst_hold()/dst_release() in ip_append_data() David Miller
2008-11-25 2:22 ` Andi Kleen
2008-11-24 11:27 ` [RFC] Could we avoid touching dst->refcount in some cases ? Andi Kleen
2008-11-24 23:36 ` David Miller
2008-11-24 23:39 ` David Miller
2008-11-25 4:43 ` Eric Dumazet
2008-11-25 5:00 ` David Miller
2008-11-26 0:00 ` [PATCH] net: release skb->dst in sock_queue_rcv_skb() Eric Dumazet
2008-11-26 0:23 ` David Miller
2008-11-26 2:04 ` David Miller [this message]
2008-11-26 7:39 ` Eric Dumazet
2008-11-26 9:08 ` David Miller
2008-12-17 11:25 ` net-next: broken IP_PKTINFO [was Re: [PATCH] net: release skb->dst in sock_queue_rcv_skb()] Mark McLoughlin
2008-12-18 3:34 ` net-next: broken IP_PKTINFO David Miller
2008-12-18 5:59 ` Eric Dumazet
2008-12-18 6:17 ` David Miller
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