From mboxrd@z Thu Jan 1 00:00:00 1970 From: zhuyj Subject: Re: performance decrease ? Date: Fri, 25 Apr 2014 16:18:31 +0800 Message-ID: <535A1A57.50007@gmail.com> References: Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ratheesh kannoth , netdev , Netfilter mailing list , "e1000-devel@lists.sourceforge.net" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: e1000-devel-bounces@lists.sourceforge.net List-Id: netdev.vger.kernel.org On 04/24/2014 06:15 PM, ratheesh kannoth wrote: > I did an experiment and this experiment gave me an unexpected result > ( for me). I would like to get any clue or hint on this. > [ ubuntu kernel version 3.11 ] > > i wrote an userpace program to create two tap devices( tap77 and tap88 > ) and will epoll on these fds. if a packet is received on tap77 fd, > it will be read() and write to tap88 fd and vice versa. Basically > this program will send pkts from tap88 to tap77 and vice versa. when > i sent 10 icmp packets (using ping ); i got rtt min/avg/max/mdev > =.825/1.006/2.052/.310 ms. > > > I modified tun_net_xmit() function in tun.c and created another > driver and ran the above test. > > tun_net_xmit() { > > skb_orphan(skb); > > if( skb->dev == tap77_dev ) skb->dev= tap88_dev > else if (skb->dev == tap88_dev ) skb->dev = tap77_dev; > > skb_reset_mac_header(skb); > skb_reset_network_header(skb); > skb_reset_transport_header(skb); > > netif_rx_ni(skb); netif_rx_ni(skb); will insert the skb into a queue. We can not make sure when this skb is handled. So use this function is not accurate to performance. Best Regards! Zhu Yanjun > } > > > i got rtt min/avg/max/mdev = .778/1.023/2.662/.549. > > > With the modified driver, Although we avoided 2 packet copies and 2 > system call, it did not result in performance > improvement ( it did decrease by a small delta ). > > Thanks, > Ratheesh > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > ------------------------------------------------------------------------------ Start Your Social Network Today - Download eXo Platform Build your Enterprise Intranet with eXo Platform Software Java Based Open Source Intranet - Social, Extensible, Cloud Ready Get Started Now And Turn Your Intranet Into A Collaboration Platform http://p.sf.net/sfu/ExoPlatform _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired