Shlrm.org Blag

I had posted previously about setting up a WRT54G-TM running OpenWRT to be the router for my network. I thought it would be the perfect router, low power consumption, low heat, no moving parts, and wifi included. Unfortunately it did not work well at all. My advanced traffic shaping configuration killed the poor thing. 200MHz is apparently insufficient hurtz to handle the large  number of interrupts for packet processing and marking. I was told it might be a driver issue, but I wasn’t aware of any other drivers that I could have loaded to offload those interrupts. So the system spent > 70% of it’s CPU time in System IRQ handling. When it was under heavy packet load, something the original router setup would’ve handled without batting an eye, it would drop connections and eventually die. It wouldn’t respond to pings, nor would it forward traffic adequately. NAT + Traffic shaping + bittorrents = DEATH. Not to mention that syslogd eventually threw the thing into a kernel panic. Oh, and the b43 driver also panicked the kernel soon after turning on the wifi.

So I’m back to the original setup, with an old (1998) left-over 2GB hard-drive, and a modified Source Mage install. It’s in good shape, with some tmpfs stuff for things that write to the disk in order to hopefully prolong the life of the disk. I took a clonezilla snapshot of it as well, so when the drive dies, I can throw in a new (also old, I have several 2 to 4 GB drives that are in the closet that still work) one, and the router will be back up in a few moments.

Whilst it was unfortunate that the router wasn’t a good fit for my particular use, perhaps I’ll find another use for it. Since there are two Serial ports trivially accessible on the device, perhaps I’ll get a GPS module and set it up in the car as a mobile automatic war-driving toy. I’ve found instructions to hook up an SD card to it as well, that would give it plenty of easy to replace storage.

It was an interesting experiment, and I’m somewhat sad it didn’t work out.

…means I can finally pause/suspend a domU vm again!

Finding this information should’ve been obvious, but for some reason it wasn’t. Maybe I had some silly mental block or something. Anyways, get the kernel source from here. Then build it for your architecture. If you want to build a 32-bit kernel for some 32-bit domUs, and you’re running on 64-bit, it’s as easy as make ARCH=i386 <target>. This does work and I’ve verified it. Had to fool a Fedora domU into beleiving that it really was a 32-bit system.

I’ve found make tarbz2-pkg to be quite handy in packaging up the kernel to be deployed.

I have verified that this works in Xen 3.4.2 on a patched 2.6.29.6 kernel.

On my Xen 4.0 test box, it fails to suspend. I’m using the blktap2 stuff, and perhaps that doesn’t pause well. As far as I understand it, that blktap2 should not affect suspending, but I’m going to test it with some logical volume based vms. I usually use the lvm backed disks anyway, but the blktap2 stuff offers some interesting features, if it were to work. Not being able to pause stuff probably isn’t good, but again, I’m not sure what’s causing it.

Apparently, that is what’s causing it. The domU will pause and unpause just fine when using an lvm backed disk, rather than the blktap2 ones. I should test a couple of other combinations to see if things like tap:aio will behave, as that’s needed for nifty things like remus.

It is time for Source Mage’s annual server fundraiser again. We’re raising enough to pay for our dedicated server that hosts our git repositories, and provides the master for our mirrors. We own that server entirely (well actually our current Project Lead does, since Source Mage isn’t a “real” organization) and it’s hosted in a co-location facility with an SLA and all that good stuff. Our costs are only about $100 a month, which isn’t too bad. This fundable should cover it in its entirety and ensure that Source Mage remains up and operational on the internet.

Incidentally, it’s also time for the Project Lead to be reelected, or a new Project Lead voted in. So if you’re a Source Mage developer and, for some strange reason, you’re reading my blog, go make a nomination if you feel like it.

http://shlrm.org/xenstats/ (original scripts here)

Now you can view the stats on who’s doing the most work in my Xen hosts. Yay.

It explodes if there’s a halted vm. It’s not built to handle the new xen 3.0 lifestyle of things. I guess I’ll be learning myself some python. Or I’ll translate it all to bash ;) I could probably do it in bash. Not that python isn’t used for everything in xen anyway. Okay, now I’m rambling.