measuring shared memory on linux (was [Fwd: Re: /proc/*/statm, exactly what does "shared" mean?)]

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Richard F. Rebel wrote:
> Hello Perrin and other modperl users,
> 
> I have forwarded an email from Hugh Dickens as a follow up on recent
> discussion of mod_perl+apache forked children and copy-on-write pages.

Thanks for pursuing that issue at the linux kernel list, Richard. As you 
have suggested it doesn't look very good.

At the same time the actual sharing is the same as before, so you still 
win from preloading things. It's just that you can't quantify it anymore.

Once we get some "official" resolution we should update the tools like 
Apache-VMonitor to reflect that discovery, in order to not mislead users.
More importantly it affects Apache::SizeLimit and Apache::GTopSizeLimit, 
which as the things are now, aren't working properly when someone limits 
on shared memory.

Can others give us an update on other OSes? I know Gtop works on BSDs and 
Solaris. Does it give the proper shared data over there? And the "manual" 
methods used by Apache::SizeLimit?

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