On Mon, 20 Mar 2000, Jesse Pollard wrote:
>On Mon, 20 Mar 2000, David Whysong wrote:
>>
>>That's very misleading. In fact if you give the overcommitted system the
>>same amount of VM, it will work just fine.
>>
>>In other words, turning off overcommit isn't what saves you. You added
>>more memory!
>
>I guaranteed that the memory allocated could be used. I didn't just add
>more memory. Just adding more memory will still allow the system to fail,
>it may take longer, it may not happen as often. But it can still happen.
The only reason your non-overcommit situation doesn't fail is because you
gave that system more memory than the overcommitted system.
In order to make a reasonable comparison, you must keep the total VM
constant. The failure modes for a non-overcommitted system are a superset
of the failure modes of an overcommitted system.
Stated another way: for a fixed quantity of virtual memory, in low memory
situations, a system without overcommit will ALWAYS have a failure before
or at the same point as an overcommitted system.
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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