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I run a batch matlab job server here at my lab, running Dapper 6.06 (for the 
LTS). One of the users has submitted a very memory-consuming job, which 
successfully crashes the server. Upon closer inspection, the crash happens like 
this:
1. I run matlab with the given file (as an ordinary, unpriveleged user)
2. RAM usage quickly fills up
3. Once the RAM meter hits 100%, the system freezes: All SSH connections freeze 
up, and while switching VTs directly on the machine works, no new processes run 
- so one can't log in, or do anything if he is logged in. (Sometimes typing 
doesn't work at all)

Note that the swap - while 7 gigs of it are available - is never used.
(The machine has 7 gigs of RAM as well)

I've tried the same on my Gutsy 32-bit box, and there was no system
freezeup - matlab simply notified that the system was out of memory.
However, it did this once memory was 100% in use - and still, swap
didn't get used at all! (Though it is mounted correctly and shows up in
"top" and "free").

So first thing's first - I'd like to eliminate the crash issue. I
suppose I could switch the server to 32-bit, but I think that would be a
performance loss, considering that it does a lot of heavy computation.
There is no reason, however, that this should happen on a 64-bit machine
anyway. Why does it?

WORKAROUND: Enabling DMA in the BIOS

** Affects: linux (Ubuntu)
     Importance: Low
         Status: Incomplete


** Tags: dapper needs-upstream-testing
-- 
System freeze on high memory usage when DMA is disabled
https://bugs.launchpad.net/bugs/159356
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