Setting ulimits is generally a good idea, because excessive memory
use is usually a sign of a bug, and it is better if the program
crashes before it forces the system to thrash its swapspace
(especially on multi-user machines)
One can set "soft" ulimits, which are generally the right thing: The
user can increase them if he really needs to, but is otherwise
protected.
Indeed, setting the virtual memory ulimit too low will cause sage to
fail starting up. Apparently, 10^5 kib is too small for sage, which
is fine:
sh-3.2$ ulimit -S -v 100000
sh-3.2$ ulimit -v
100000
sh-3.2$ sage
----------------------------------------------------------------------
| Sage Version 4.4.4, Release Date: 2010-06-23 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
[...]
ImportError: /usr/local/sage/4.4.4/local/lib/python2.6/lib-dynload/
fcntl.so: failed to map segment from shared object: Cannot allocate
memory
However, if we set a more reasonable bound (10^6 kib, roughly a gig),
sage does start up without problem, but as you can see, it wipes the
soft virtual memory limit!
sh-3.2$ ulimit -S -v 1000000
sh-3.2$ ulimit -v
1000000
sh-3.2$ sage
----------------------------------------------------------------------
| Sage Version 4.4.4, Release Date: 2010-06-23 |
| Type notebook() for the GUI, and license() for information. |
----------------------------------------------------------------------
sage: import os
sage: os.system("ulimit -v")
unlimited
0
Is this intentional? Does someone know how to turn this off? Our
students and the people who share computers with them greatly benefit
from programs crashing quickly instead of bothering other people.
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