From: Eric Dumazet <eric.dumazet@gmail.com>
To: Junchang Wang <junchangwang@gmail.com>
Cc: netdev@vger.kernel.org
Subject: Re: Question about __alloc_skb() speedup
Date: Sat, 04 Dec 2010 15:47:38 +0100 [thread overview]
Message-ID: <1291474058.2806.96.camel@edumazet-laptop> (raw)
In-Reply-To: <20101204141826.GA5830@Desktop-Junchang>
Le samedi 04 décembre 2010 à 22:18 +0800, Junchang Wang a écrit :
> I added the prefetchw() in pktgen as follows:
>
> diff --git a/net/core/pktgen.c b/net/core/pktgen.c
> index 2953b2a..512f1ae 100644
> --- a/net/core/pktgen.c
> +++ b/net/core/pktgen.c
> @@ -2660,6 +2660,7 @@ static struct sk_buff *fill_packet_ipv4(struct net_device *odev,
> sprintf(pkt_dev->result, "No memory");
> return NULL;
> }
> + prefetchw(skb->data);
>
> skb_reserve(skb, datalen);
>
> This time, I can check it without rebooting the system. The performance
> gain is 4%-5%(stable). Does 4% worth submitting it to the kernel?
Yes I believe so, pktgen being very specific, but I have few questions :
Is it with SLUB or SLAB ?
How many buffers in TX ring on you nic (ethtool -g eth0) ?
What is the datalen value here ? (you prefetch, then advance skb->data)
32 or 64bit kernel ?
How many pps do you get before and after patch ?
Thanks
next prev parent reply other threads:[~2010-12-04 14:47 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-03 10:14 Question about __alloc_skb() speedup Junchang Wang
2010-12-03 10:50 ` Eric Dumazet
2010-12-04 14:18 ` Junchang Wang
2010-12-04 14:47 ` Eric Dumazet [this message]
2010-12-04 14:49 ` Eric Dumazet
2010-12-05 10:56 ` Junchang Wang
2010-12-05 16:49 ` Eric Dumazet
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