Review request for 5049299

Florian Weimer fweimer at
Fri May 29 10:47:06 UTC 2009

* Andrew Haley:

> Florian Weimer wrote:
>> * Andrew Haley:
>>>> The latter leads to problems if the maximum heap size is relatively large.
>>>> Currently, -Xmx is reserved, and some software fails to build on
>>>> vm.overcommit_memory systems due to this.
>>> I don't get it.  Why would overcommit cause some software to fail to
>>> build?  I can understand it failing if overcommit was turned off.
>> Sorry, I meant to write "vm.overcommit_memory=2".
> Well, the system is doing what the user asked it to do.  -Xmx means
> "please reserve this memory for me, Hal"; if the memory isn't there,
> then it's surely quite reasonable for Hal to respond "I'm sorry Dave,
> I can't do that."

Well, I thought -Xms means that.  An untuned VM is not expected to hit
the -Xmx limit.  At least this is what I see in practice, and to me
this is the distinction expressed between the -Xmx and -Xms flags.

Reserving the -Xms heap portion does make sense, though.

Florian Weimer                <fweimer at>
BFK edv-consulting GmbH
Kriegsstraße 100              tel: +49-721-96201-1
D-76133 Karlsruhe             fax: +49-721-96201-99

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