netdev - Re: [PATCH v4] net: batch skb dequeueing from softnet input_pkt

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <m2n412e6f7f1004220103g140ef833wb41105a491e75ae1@mail.gmail.com>
Date:	Thu, 22 Apr 2010 16:03:21 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Stephen Hemminger <shemminger@...tta.com>,
	"David S. Miller" <davem@...emloft.net>, jamal <hadi@...erus.ca>,
	Tom Herbert <therbert@...gle.com>, netdev@...r.kernel.org
Subject: Re: [PATCH v4] net: batch skb dequeueing from softnet input_pkt_queue

On Thu, Apr 22, 2010 at 3:21 PM, Eric Dumazet <eric.dumazet@...il.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@...il.com)
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html