On 13 Mar 2000, Rask Ingemann Lambertsen wrote:
>
>Apps would be told that the system is out of memory instead of just
>getting a SIGKILL'ed out of the blue sky. Apps getting NULL from
>malloc() can react appropriately, such as saving your files to disk,
>trying again a little later or just exiting if that is acceptable for
>what the app was doing. Apps getting SIGKILL will take your unsaved work
>with them in the fall.
Ok, so my big gravitational simulation gets NULL from malloc and decides
to save it's work and exit. Uh-oh, time to demand-load a page of
executable code that had been discarded, so we can save the data. Hmm, but
we're out of memory...
Even if that succeeds, or there is a foolish "no overcommit" policy, we
need disk buffers. What if the program was told to save output to a SCSI
device, and the kernel needs to load the driver module? We're out of
memory! Even if we all build non-modular kernels, the kernel does some
dynamic memory allocation.
As for "trying again a little later", that leaves you with an unresponsive
and unusable system in many cases.
And please explain why my simulation -- that may have started many weeks
(or months) ago -- should "just exit" because some random 5-minute old
Mathematica process went and allocated half a gigabyte of memory?
Dave
David Whysong dwhysong@physics.ucsb.edu
Astrophysics graduate student University of California, Santa Barbara
My public PGP keys are on my web page - http://www.physics.ucsb.edu/~dwhysong
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