Messages in this thread | | | Date | Sat, 25 Mar 2000 16:45:10 -0800 (PST) | From | David Whysong <> | Subject | Re: Endless overcommit memory thread. |
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On Sat, 25 Mar 2000, Linda Walsh wrote: >"Richard B. Johnson" wrote: > >> Even if the perfect operating system kept some virtual RAM for >> 'root' to log-in. It has no idea of what programs root would >> want to execute. Eventually, it will fail with an out-of memory >> condition. >--- > Having no idea of what programs root would execute doesn't mean >you can't reserve sufficient memory for a shell, a ps and a kill. >But if my machine runs out of processes and I can't log in -- I have >little choice but to hit the RESET button.
You could use alt-sysrq to kill some tasks from the console, if you have one. :-)
> By allowing 'overcommit', you end up in a situation where now your >90M process touches the last of its memory -- and it isn't there, so.... >it SEGFAULT's because the memory mapper can't the address to a physical \ >object?
It gets killed because the sysadmin didn't put enough memory in the machine. Which has nothing to do with overcommit...
> If you allow overcommit, you can have *either* the SEGFAULT behavior >*or* the no-mem/locked out (process touches everything up front). >If you disallow overcommit, you reduce the possible behaviors to 1.
You're confusing OOM situations with overcommit. OOM can happen without overcommit.
>The problem is that suppose the process allocates it's memory -- with >the 'overcommit' you have a system where it is hard to predict *what* >will fail. Will it be a system process? A deamon? It's a >low-integrity system because you can't figure out the behavior of >failure in advance.
Predicting what will fail has nothing to do with overcommit. It depends on the kernels OOM behavior.
> David's killing demon is fine for a user-space/level solution, >but the kernel should default to the high-integrity option.
Which is Rik van Riel's patch, or something very much like it.
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 DSS PGP Key 0x903F5BD6 : FE78 91FE 4508 106F 7C88 1706 B792 6995 903F 5BD6 D-H PGP key 0x5DAB0F91 : BC33 0F36 FCCD E72C 441F 663A 72ED 7FB7 5DAB 0F91
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