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From: Qin Chuanyu <qinchuanyu@huawei.com>
To: <jasowang@redhat.com>, "Michael S. Tsirkin" <mst@redhat.com>,
	"Anthony Liguori" <anthony@codemonkey.ws>,
	KVM list <kvm@vger.kernel.org>, <netdev@vger.kernel.org>
Subject: 8% performance improved by change tap interact with kernel stack
Date: Tue, 28 Jan 2014 16:14:12 +0800	[thread overview]
Message-ID: <52E766D4.4070901@huawei.com> (raw)

according perf test result，I found that there are 5%-8% cpu cost on 
softirq by use netif_rx_ni called in tun_get_user.

so I changed the function which cause skb transmitted more quickly.
from
	tun_get_user	->
		 netif_rx_ni(skb);
to
	tun_get_user	->
		rcu_read_lock_bh();
		netif_receive_skb(skb);
		rcu_read_unlock_bh();

The test result is as below:
	CPU: Intel(R) Xeon(R) CPU E5620  @ 2.40GHz
	NIC: intel 82599
	Host OS/Guest OS:suse11sp3
	Qemu-1.6
	netperf udp 512(VM tx)
	test model: VM->host->host

	modified before : 2.00Gbps 461146pps
	modified after  : 2.16Gbps 498782pps

8% performance gained from this change,
Is there any problem for this patch ?


             reply	other threads:[~2014-01-28  8:15 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-01-28  8:14 Qin Chuanyu [this message]
2014-01-28  8:34 ` 8% performance improved by change tap interact with kernel stack Michael S. Tsirkin
2014-01-28  9:14   ` Qin Chuanyu
2014-01-28  9:41     ` Michael S. Tsirkin
2014-01-28 10:19       ` Qin Chuanyu
2014-01-28 10:33         ` Michael S. Tsirkin
2014-01-28 16:58           ` Stephen Hemminger
2014-01-28 17:18             ` Michael S. Tsirkin
2014-01-29  7:41           ` Qin Chuanyu
2014-01-29  7:56             ` Michael S. Tsirkin
2014-01-28 16:56     ` Rick Jones
2014-01-28 14:49 ` Eric Dumazet
2014-01-29  7:12   ` Qin Chuanyu
2014-02-11 13:21   ` Qin Chuanyu

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