Review request for 5049299 (original) (raw)

Andrew Haley aph at redhat.com
Sun May 24 09:16:19 UTC 2009

Martin Buchholz wrote:

I did a little research.

The overcommitment policy on Linux is configurable http://lxr.linux.no/linux/Documentation/vm/overcommit-accounting Of course, almost everyone will use the default "heuristic" policy, and in this case the COW memory after fork() is subject to overcommit accounting, which may cause the fork to fail.

Sure, it may, but I don't think it's at all common.

http://lkml.indiana.edu/hypermail/linux/kernel/0902.1/01777.html If a solution using clone(CLONEVM ...) can be made to work, subprocess creation will be a little cheaper and significantly more reliable.

Maybe, but I think that needs to be measured before any changes are made. I'm not opposed to such a change that makes a real improvement, but I'm not convinced it will. As usual, I'm happy to be proved wrong.

There may be a kernel bug in the case described in the mail above: it certainly should be possible to fork a 38 GB process on a system with 64 GB RAM. If so, I expect that this will be fixed long before any Java VM change makes it into production.

Andrew.

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