Swap Performance in Linux

GizmoDuck writes "I'm working in a computational chemistry lab, and we find ourselves using memory and CPU hogs like Amber and Gaussian. The CPU hogging isn't a problem, thanks to Condor, but when submitting one of the jobs that request (and pretty much require) all the physical RAM in the machines, Linux promptly starts swapping so hard that the mouse pointer in X stops moving, NFS and NIS halt, and things don't get back to normal for five minutes. I've tried toying a bit with the settings in /proc/sys/vm/kswapd to no avail. I've done some poking around on the 'net looking for answers. Faster disks and swap partitions at the beginning of the drive aren't really an option at this point. I haven't found a good solution yet. I was wondering if the /. community has any input on how to keep the system from locking during periods of necessarily high swap activity?"

Comments

Try preemtable kernel patch...

[PaulBu]

It should improve interactive performance (i.e., your mouse will start moving again :) ) when load is high. Also, running your background process nice'ed will be helpful.

You might also consider a crazy idea of having swap file on NFS -- you'll get (if your network is decent) almost the same bandwidth as you get when accessing (older) disk, but much higher latency (this will put your background process in disadvantage compared to your interactive processes).

Hope this helps.

Paul B.

You're out of luck

[afay]

Unfortunately, you're out of luck. The current linux VM (in later 2.4 series) is fine for low to medium load systems but falls apart on high load systems. The previous VM (early 2.4 series) is a good design but isn't really ready for production.

I would suggest buying more RAM (it's cheap) if you aren't already maxed at 4 gigs (x86). Alternatively switch to FreeBSD which has a very stable efficient VM. Any source should recompile without too much trouble and it can run linux binaries at almost full speed!

Shut down X?

[swillden]

Do you really have to be using the machine while it's calculating? If not, what about shutting down X and any other memory-hogging system components? Unlike on Windows you do have the option of turning off that expensive GUI.