On Mon, 15 Sep 2003, btt wrote:
> I see... so does this also include functions in shared libraries? Like
> if libc.so is already in memory for another process, then do all other
> processes that use libc share the memory addresses of the various
> functions in libc? And are the sizes of the shared functions included
> in a processes SIZE? Or is the whole libc's size included? Does that
> even make sense? :p
Actually, to be honest, I'm not sure how shared library usage is
calculated in Linux (I know more about Solaris and BSD internals).
To be sure, there's only one copy of a shared library in RAM at a time,
and various processes map that copy into their address space. It seems
that Linux top/ps have a SHARE or SHR statistic, which might represent
what fraction of your RSS consists of shared mappings. Just a random
guess, but that theory does seem to jive with what I see on a couple Linux
boxes here. <shrug>
Solaris has a neat command called pmap(1) that will give you the low-down
on the address space mappings for a given process. Don't know if Linux
has anything equivalent.
> Yeah, I have a mysql process that's using like 81,000 SIZE, but like
> 6,000 RSS.
That's probably a file being mmap()'ed by MySQL. Since the backing store
for that mapping is a file, it doesn't take any physical RAM (this isn't
true under all circumstances though).
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