Review request for 5049299

[Andrew Haley]

Martin Buchholz wrote:
> On Fri, May 22, 2009 at 15:13, Michael McMahon <Michael.McMahon at sun.com>wrote:
> 
>> Martin,
>>
>> Thanks. Great comments. Just a few comments of my own
>> on a couple of points.
>>
>> 1. Linux won't benefit from this change as much as solaris, since due to
>> its
>>   "memory overcommit" architecture, it doesn't suffer from the problem (so
>> much)
>>    in the first place (though memory overcommit causes some problems of its
>> own).
>>    Nevertheless, maybe it could simplify the code a bit if we use
>> posix_spawn() on Linux
>>    as well. So, I will look into that.
> 
> Any company running server farms (think "Sun" or "Google")
> would like to "bin-pack" as many processes as possible onto them,
> and transient doubling of process size is a big problem in such an
> environment.  Think of this as a
> saving-the-planet-from-global-warning feature.

But those running Linux won't benefit from such a change because
on Linux there is no transient doubling of process size: all that happens
is that the page table entries in the new process are mapped copy on write.
The extra pages count towards the overcommit limit, but that's wholly
artifical.

Andrew.