Re: [PATCH] processes with shared vm

[Andi Kleen <ak@suse.de>]

Terje Eggestad <terje.eggestad@scali.no> writes:

> I figured out that it's difficult to find out from /proc
> which processes that share VM (created with clone(CLONE_VM)). 
> 
> made a patch that adds in /proc/<pid>/status a VmClones field that tells
> how many proc that uses the same VM (mm_struct).  if there are clones I
> add another field VmFirstClone with the pid of clone with the lowest
> pid. 
> 
> Needed for things like gtop that adds mem usage of groups of proc, or
> else they add up the usage of SIZE and RSS of threads.
> 
> The patch need to be applied to linux/fs/proc/array.c

The basic idea is a good one (I have written a similar thing in the past ;)
Your implementation is O(n^2) however in ps, which is not acceptable.
Much better is it to add a new field to mm_struct that gets initialised
on first creation with the pid, and adding a place holder in pid hash
if that process goes away and the mm_struct is still there to avoid pid
reuse (or alternatively link task_structs to mms and always use the pid of
the first entry)

-Andi