From: Changli Gao <xiaosuo@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Stephen Hemminger <shemminger@vyatta.com>,
"David S. Miller" <davem@davemloft.net>, jamal <hadi@cyberus.ca>,
Tom Herbert <therbert@google.com>,
netdev@vger.kernel.org
Subject: Re: [PATCH v4] net: batch skb dequeueing from softnet input_pkt_queue
Date: Thu, 22 Apr 2010 16:03:21 +0800 [thread overview]
Message-ID: <m2n412e6f7f1004220103g140ef833wb41105a491e75ae1@mail.gmail.com> (raw)
In-Reply-To: <1271920877.7895.4757.camel@edumazet-laptop>
On Thu, Apr 22, 2010 at 3:21 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> Jamal perf reports show lock contention but also cache line ping pongs.
>
> Yet, you keep a process_queue_len shared by producers and consumer.
>
> Producers want to read it, while consumer decrement it (dirtying its
> cache line) every packet, slowing down the things.
>
>
> The idea of batching is to let the consumer process its local queue with
> no impact to producers.
>
> Please remove it completely, or make the consumer zero it only at the
> end of batch processing.
>
> A cache line miss cost is about 120 cycles. Multiply it by 1 million
> packet per second...
>
OK, I'll remove it, and update the input_pkt_queue only before
process_backlog returns.
--
Regards，
Changli Gao(xiaosuo@gmail.com)
prev parent reply other threads:[~2010-04-22 8:03 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-04-22 5:51 [PATCH v4] net: batch skb dequeueing from softnet input_pkt_queue Changli Gao
2010-04-22 6:18 ` Stephen Hemminger
2010-04-22 6:30 ` Changli Gao
2010-04-22 7:21 ` Eric Dumazet
2010-04-22 8:03 ` Changli Gao [this message]
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