netdev - Re: 8% performance improved by change tap interact with kernel stack

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: Windows password security audit tool. GUI, reports in PDF.

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

Message-ID: <52E77506.1080604@huawei.com>
Date:	Tue, 28 Jan 2014 17:14:46 +0800
From:	Qin Chuanyu <qinchuanyu@...wei.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
CC:	<jasowang@...hat.com>, Anthony Liguori <anthony@...emonkey.ws>,
	KVM list <kvm@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: 8% performance improved by change tap interact with kernel stack

On 2014/1/28 16:34, Michael S. Tsirkin wrote:
> On Tue, Jan 28, 2014 at 04:14:12PM +0800, Qin Chuanyu wrote:
>> 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 ?
>
> I think it's okay - IIUC this way we are processing xmit directly
> instead of going through softirq.
> Was meaning to try this - I'm glad you are looking into this.
>
> Could you please check latency results?
>
netperf UDP_RR 512
test model: VM->host->host

modified before : 11108
modified after  : 11480

3% gained by this patch



--
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