netdev - Re: vxlan/veth performance issues on net.git + latest kernels

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Date:	Fri, 6 Dec 2013 11:06:45 +0200
From:	Or Gerlitz <or.gerlitz@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Alexei Starovoitov <ast@...mgrid.com>,
	David Miller <davem@...emloft.net>,
	Joseph Gasparakis <joseph.gasparakis@...el.com>,
	Jerry Chu <hkchu@...gle.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	Eric Dumazet <edumazet@...gle.com>,
	Pravin B Shelar <pshelar@...ira.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: vxlan/veth performance issues on net.git + latest kernels

On Wed, Dec 4, 2013 at 3:23 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> skb->dev is in the first cache line, where we access skb->next anyway.
> I could use skb->cb[] like the following patch :

Hi Eric, I applied on the net tree the patch you posted yesterday
"net: introduce dev_consume_skb_any()" along with the network drivers
part of this patch, unless I got it wrong, I assume both pieces are
needed?

So I re-run the vxlan/veth test that we suspect goes through packet drops on TX.

With the patches applied I have almost no samples of that event

$ ./perf report -i perf.data

Samples: 89  of event 'skb:kfree_skb', Event count (approx.): 89
+  39.33%  ksoftirqd/2  [kernel.kallsyms]  [k] net_tx_action

                    ?
+  28.09%      swapper  [kernel.kallsyms]  [k] net_tx_action

                    ?
+  28.09%         sshd  [kernel.kallsyms]  [k] net_tx_action

                    ?
+   2.25%      swapper  [kernel.kallsyms]  [k] kfree_skb

                    ?
+   1.12%  kworker/2:2  [kernel.kallsyms]  [k] net_tx_action

                    ?
+   1.12%        iperf  [kernel.kallsyms]  [k] net_tx_action

 ./perf report -i perf.data --sort dso,symbol
Samples: 89  of event 'skb:kfree_skb', Event count (approx.): 89
+  97.75%  [kernel.kallsyms]  [k] net_tx_action
+   2.25%  [kernel.kallsyms]  [k] kfree_skb
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