User Mode Linux performance tuning
I haven’t posted for a while, partly because I’ve been on vacation, but particularly because the UML instance I’m using has been behaving… poorly. Every time I post an article it seems to hang for quite some time (minutes, not seconds). I’m starting to get some ideas about what my problems might be.
So, it has taken me a while, but a few things have become apparent to me. First, and most likely the biggest contributor, is that I’m running a fairly new host glibc with a fairly old host kernel and then on top of that I’ve got a fairly new UML kernel. In particular, I suspect this is running in to problems with various bugs UML has had with NPTL.
On top of this, I realized I’ve had my UML kernels defaulting to using completely fair queuing, which is probably counter productive. It’s probably more efficient to get rid of queuing altogether and let things go right to the host, otherwise you get all kinds of ugliness from having two levels of IO scheduling going on.
Anyway, I’ve changed my IO scheduling, and hopefully this weekend I’ll be able to put together a new set of host/UML kernels built on 2.6.20 or maybe even newer (if I dare).
[Crossing fingers]