Slow network access on Windows XP Guest

[gworboys]

I am in the process of building an entirely new system for my development work. Previously I have been using VMWare Workstation over Windows XP primarily for testing software, I am now trying to build a system using VMWare Workstation of Linux - with all "real" work taking place in VMs. To that end I have built:

Intel Quad-core (Q9400) with 8GB of RAM on an Asus mobo with dual Marvell Gigabit LAN (and NVidia 9600 GPU), running Ubuntu v8.10 x86_64 and VMWare Workstation v6.5.0 build-118166. Only one of the network adapters is currently in use, the other is defined in the Ubuntu host but not connected to anything yet.

I set-up a Windows XP SP3 guest with 1Gb of RAM and 2-CPUs - intending this to be used for software development which will make use of multiple CPUs. It is running VMTools and using the "VMware Accelerated AMD PCNet Adapter". Networked to the first (only active) network using bridged networking. What I found was that connecting to another XP workstation on the LAN (not on the same host) was very slow. Host-to-Guest seemed fast... at least the shared folders part was fine, but copying files from shares on a separate workstation (the remote is XP on the hardware not a VM) was very slow.

I first noticed the problem while viewing some photos using Irfanview (2.5Mb JPEGs, 10mpix), but it was definitely a network issue as just copying the files was very slow too. Simply flicking from photo to photo in Irfanview was taking around 6 seconds, viewing the same files locally took less than a second (and was effectively instantaneous if done on the host). I noticed that during the copy 1 of the 2 cpus was running at close to 100% for 5 or so seconds. Even just displaying folders (in Explorer) on this remote box was very slow and CPU intensive.

I tried various things I had seen on this list; disabling the host-only and NAT adapters, "ethtool -K tso off" on the Linux host, reducing the memory from 1024Mb to 900Mb, disabling firewall and av software in the guest, but none made any difference.

What has eventually "solved" the problem was removing virtual SMP by taking the definition back from 2 CPUs to just 1 CPU. (I did not change the XP installation so it is still showing as ACPI Multiprocessor CPU.)

I have read the VMWare docs that indicate virtual SMP is best on ESX, so maybe this problem is to be expected when trying it on Workstation... anyway I thought I would post this here. If VMWare think it may be a problem I am happy to offer more information. If others come across the issue this post may help to save them some time.

[nextech]

I had a similar problem, I posted the solution to this problem here:

http://communities.vmware.com/message/1191790#1191790

I hope this helps, I believe this should solve your problem. If you find this answer helpful, please do take the time to award me the "Correct Answer" points.

Thank-you!

Mark

[gworboys]

Hi Mark, I thank your for the response to my post... I happened across it because I still have the same problem despite the release of VMware Workstation v6.5.2 (official support for Ubuntu v8.10).

The command mentioned in my original post ("ethtool -K tso off") is the closest Linux equivalent I have been able to find what you describe in your thread. This is disables "TCP Segmentation Offload" - whether that is identical to the Offload's you describe is difficult to say. ethtool has other offload controls too (checksums etc) and turning those off made no difference either.

I was able to see almost exactly your problem when I set aside a small partition and installed a WinXP 32bit host (do not have a 64bit XP available). I installed VMware Wks v6.5 and ran the WinXP 32bit guest. The guest with a single CPU configuration had awful network performance (but in this case the CPU load does not appear to be significant). When I changed the host network adapter setting you describe the network problem goes away (I did not even have to reboot anything). Note that the same guest configured to 2-cpus on this WinXP host did not experience any network response time problems - with or without that offload setting.

So my problem is definitely the host (Ubuntu or VMware on Ubuntu)... something causes a bottleneck that drives the CPU crazy for network access when the guest is configured to 2-cpus (virtual SMP).

Sorry I cannot give you points for a correct answer -I would like a correct answer

I am considering whether I should revert the hosts to Windows (buy myself some 64bit licenses). I had been hoping the performance issues would be resolved with official support for Ubuntu v8.10, so I waited... but testing 6.5.2 shows that the problem remains.