- Roundtable - muug.ca

NIC performance with iperf
by Adam Thompson 18 Apr '10

18 Apr '10

FYI. Windows networking sucks, across all versions of Windows. (At least, at Gigabit speeds, it does.) Between my Windows 7 PC (3.06Ghz HT Pentium 4, Intel PRO 1000/MT Desktop Adapter [82540EM]) and Gentoo Linux server (2 x 2.2GHz Xeon [P4 core], PCI-X [64-bit,66Mhz] Intel PRO 1000/MT Dual-Port Server Adapter [82546EB]) Using "iperf -s" and "iperf -c 192.168.x.x", I get - consistently - between 238Mbps and 250Mbps **in both directions**. Interesting to note is that the Windows 7 PC is CPU-limited on both sending and receiving, despite having all the offload and acceleration features turned on. Simultaneously, the Gentoo box sees a spike on one CPU... to 1%. In UDP traffic, however, I see a startling asymmetry: PC-to-Linux can only send UDP at ~50Mbps, Linux-to-PC sends UDP at ~475Mbps. WTF? I also tried the Parallel option, which runs multiple streams in parallel. Results are consistent, aggregate bandwidth is still only about 260Mbps. Two streams pegs both logical (HT) CPUs on the client at ~95% utilization. I tried enabling and disabling both the Windows Firewall and my AV software, which made essentially no difference at all. Then I also tried running the same set of tests from a Windows 2003 R2 server (2 x 2.13GHz Athlon MP, PCI-X [64-bit,66Mhz] Broadcom NetXtreme [BCM57xx]) N.B. this is the same model of motherboard Kevin is using in his Linux server. and observed slightly better throughput to the Linux server: about 380Mbps. Still better was Linux-to-W2K3R2, at about 440Mbps. UDP performance was similar to Kevin's results, at 103Mbps W2K3-to-Linux & 950Mbps Linux-to-W2K3. CPU utilization on the W2K3R2 box exhibited similar properties as the Win7 client, although none of the tests actually managed to max out either CPU, instead peaking at about 70% utilization. Just for kicks, I ran a test between a RHEL5 VM (under VMWare ESXi 4.0U1, VMXNET adapter) and my Linux server... 920+ Mbps every time! Of course, that number may be suspect since the UDP test reports speeds of 45.3Gbps :-). Conclusion: the culprit is the Windows networking stack. Note that W2K3R2 is supposed to support zero-copy TCP offload, theoretically allowing network communications at wirespeed with extremely low latency. So much for that idea... -Adam Thompson <athompso(a)athompso.net> (204) 291-7950

4 4

printing from an iPad to an HP printer
by Adam Thompson 16 Apr '10

16 Apr '10

It appears that Apple has developed, in conjunction with HP, entirely new printing technology for iPad applications. http://www.theformgroup.com/about/blog/2010/04/how-to-print-from-an-ipad :-) -Adam Thompson <athompso(a)athompso.net> (204) 291-7950

1 0

Re: [RndTbl] Multiple simultaneous SSH connections
by Adam Thompson 16 Apr '10

16 Apr '10

'twas I who needed a solution. The problem with cfengine (and possibly puppet?) is that I cannot install any software on the target servers and have to keep my on-system footprint to an absolute minimum. I do, however, have one server of my own (so to speak) in the network that I can use for non-invasive monitoring, which can include running commands remotely via SSH. -Adam

2 1

squid caching of Windblows Updates
by Trevor Cordes 16 Apr '10

16 Apr '10

As discussed at the Apr meeting, here is my solution for having squid cache your Windblows (XP, mainly but should work for Vista/7) updates downloads. I have just verified this is still working at all my customer sites by looking at the squid access logs and seeing HITs for the big CAB files from windowsupdate.com. This confirms what I have always been seeing while manually doing updates. The magic line you require in your squid.conf is: refresh_pattern http://www.download.windowsupdate.com/ 0 80% 525600 reload-into-ims (no wrapping on the above line) If someone wants my entire squid.conf, let me know. It's setup for a pretty common case where you want to squid all of your internal (192.168.*) computers. The only other major thing is make sure you have a pretty big squid cache and max object size. I recommend at least 3GB. If you have tons of disk, make it 50G or something. More never hurts. I use: cache_swap_low 94 cache_swap_high 97 maximum_object_size 800000 KB Which should nicely handle the Win Update case we're trying to achieve. Now, to make it so you don't have to configure ANYTHING on a stock WinXP box to make it use squid: Make a file on your web server's document root (ie: /var/www/html or similar) called wpad.dat. Make it world readable. Populate it thusly: <? header("Content-type: application/x-ns-proxy-autoconfig"); ?> function FindProxyForURL(url, host) { if ( isPlainHostName(host) || dnsDomainIs (host,"tecnopolis.ca") || dnsDomainIs (host,"nocachingdomain.whatever") || shExpMatch (host,"192.168.*") || shExpMatch (url ,"*windowsupdate.microsoft.com/*.js*") || shExpMatch(url ,"*windowsupdate.microsoft.com/*.asp*") ) return "DIRECT"; if (url.substring(0, 5) == "http:" || url.substring(0, 4) == "ftp:" || url.substring(0, 7) == "gopher:") return "PROXY 192.168.1.1:8080; DIRECT"; return "DIRECT"; } Tweak the DIRECT domain/IP exclusions in the first if set. Change the 192.168.1.1 to your squid server's IP. Change the 8080 to whatever port you want to have squid listen to. There's a more standard default port, but I use 8080 as that's what Shaw used when I signed up ages ago and it's easy to remember :-) You also require some funky apache config to make it work: <VirtualHost *:80> ServerName wpad.tecnopolis.ca ServerAlias wpad DocumentRoot /var/www/html Alias /wpad.dat /var/www/html/wpad.dat </VirtualHost> (may be a bit redundant, but I am editing my slightly more complex setup to be usable by others) Note, wpad.dat only applies to IE (Internet Exploder) to make Nutscrape-based browsers (Fireflax) you need to make another identical file (hardlink?) called proxy.pac and do some more funky apache stuff: <VirtualHost *:80> ServerName proxy.tecnopolis.ca ServerAlias proxy DocumentRoot /var/www/html Alias /wpad.dat /var/www/html/wpad.dat Alias / /var/www/html/proxy.pac </VirtualHost> More redundancy, but trust me, getting this stuff to work is mystical voodoo so cover all your bases. AND, obviously add proxy and wpad as CNAMEs in your DNS server's config! They must resolve to your web server's IP. Lastly, XP by default has the "autodetect proxy settings" enabled in IE, so you literally have to do nothing to have your entire network magically start using the proxy. If it doesn't seem to be working, double-check that IE indeed has that option enabled (Tools, connections, lan settings). Like I said, it's been 10 years since I set this up and last looked it it, so hopefully I'm not overlooking some important point. It literally has worked all these years without tweaking on dozens of servers. 3 cheers for UN*X and it's stability of configuration and migration!

5 10

Re: [RndTbl] squid caching of Windblows Updates
by Adam Thompson 15 Apr '10

15 Apr '10

IIRC the DHCP option works for OS X.

1 0

Network performance tuning
by Kevin McGregor 15 Apr '10

15 Apr '10

I've been trying to narrow down where my performance bottleneck(s) is (are). I just ran "iperf" from a Windows PC (XP SP3) to my Ubuntu 9.10 server. With iperf in "server" mode on the PC, and the client running on the Ubuntu machine, I get 0.0-60.0 sec 4.23 GBytes 606 Mbits/sec Reversed (iperf "server" running on Ubuntu server, client running on the PC), I get 0.0-60.0 sec 1.13 GBytes 162 Mbits/sec Wha...?? Both client and server runs on the PC report TCP window size to be 8 KB, but the Linux client reports 22.4 KB and the Linux server reports 85.3 KB. Increasing that to 256K on both ends has little effect. Does anyone have any suggestions? The Windows NIC is a Realtek RTL8169/8110 Family Gigabit Ethernet; the Ubuntu server is using the Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01). Time to replace a NIC or two? Kevin

4 11

Multiple simultaneous SSH connections
by Gilbert E. Detillieux 14 Apr '10

14 Apr '10

At last night's meeting, during the round-table discussion, someone asked about setting up simultaneous SSH connections to multiple host sytsems. Here's the program I was thinking of... ClusterSSH: http://sourceforge.net/projects/clusterssh/ For MacOS X, there's also csshX that interfaces to the Terminal.app... csshX: http://code.google.com/p/csshx/ Adam also mentioned PSSH... http://www.theether.org/pssh/docs/0.2.3/pssh-HOWTO.html http://www.theether.org/pssh/ Both PSSH and Cluster SSH are described in the following article, along with yet another option called Multixterm... http://www.ubuntugeek.com/execute-commands-simultaneously-on-multiple-serve… Hope that helps! -- Gilbert E. Detillieux E-mail: <gedetil(a)muug.mb.ca> Manitoba UNIX User Group Web: http://www.muug.mb.ca/ PO Box 130 St-Boniface Phone: (204)474-8161 Winnipeg MB CANADA R2H 3B4 Fax: (204)474-7609

2 1

PCIe interrupt assignments
by Kevin McGregor 07 Apr '10

07 Apr '10

I have an 8-port SATA disk controller in a PCIe slot (thanks, Trevor!), and it seems to be sharing an interrupt. I'm running Ubuntu Server 9.10 64-bit. Is there some way to arrange for it to have its own interrupt, unshared? Kevin

3 3

MUUG Meeting, April 13, 7:30pm -- A Trio of RTFM!
by gedetil＠cs.umanitoba.ca 06 Apr '10

06 Apr '10

The Manitoba UNIX User Group (MUUG) will be holding its next monthly meeting on Tuesday, April 13. The meeting topic for this month is as follows: A Trio of RTFM! Weve had a lot of positive feedback to our previous RTFM presentations, so this month, were offering you a trio of them! To start, Gilbert Detillieux will be introducing the grep family of commands (grep, egrep and fgrep) including a brief look at regular expression syntax and usage. Next up, Michael Doob will present the sed command, showing you how to take regular expressions a little further. Finally, Mark Jenkins will present the smartctl command, for monitoring hard disk status and health. The group holds its general meetings at 7:30pm on the second Tuesday of every month from September to June. (There are no meetings in July and August.) Meetings are open to the general public; you don't have to be a MUUG member to attend. ********************************************************************** Please note our meeting location: The IBM offices, at 400 Ellice Ave. (between Edmonton and Kennedy). When you arrive, you will have to sign in at the reception desk, and then wait for someone to take you (in groups) to the meeting room. Please try to arrive by about 7:15pm, so the meeting can start promptly at 7:30pm. Don't be late, or you may not get in. (But don't come too early either, since security may not be there to let you in before 7:15 or so.) Non-members may be required to show photo ID at the security desk. Limited parking is available for free on the street, either on Ellice Ave. or on some of the intersecting streets. Indoor parking is also available nearby, at Portage Place, for $5.00 for the evening. Bicycle parking is available in a bike rack under video surveillance located behind the building on Webb Place. ********************************************************************** For more information about MUUG, and its monthly meetings, check out their Web server: http://www.muug.mb.ca/ Help us promote this month's meeting, by putting this poster up on your workplace bulletin board or other suitable public message board: http://www.muug.mb.ca/meetings/MUUGmeeting.pdf -- Gilbert E. Detillieux E-mail: <gedetil(a)muug.mb.ca> Manitoba UNIX User Group Web: http://www.muug.mb.ca/ PO Box 130 St-Boniface Phone: (204)474-8161 Winnipeg MB CANADA R2H 3B4 Fax: (204)474-7609

1 0

Potentially long cron jobs
by Kevin McGregor 01 Apr '10

01 Apr '10

I want to run something via cron which will take anywhere from less than a minute to a day or so (possibly). Most of the time it will be well under an hour, and I'd like it to run hourly, except if it's still running, in which case nothing more need be done. What the best way to do that? Kevin

5 4