Messages in this thread | | | Date | Wed, 29 Aug 2007 15:14:32 +0800 | From | Fengguang Wu <> | Subject | Re: How to find out how many other processes share VM with $PID? |
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On Tue, Aug 28, 2007 at 09:00:41PM +0100, Denys Vlasenko wrote: > On Tuesday 28 August 2007 01:10, Fengguang Wu wrote: > > > > There is a nice LWN article on this issue: > > > > ELC: How much memory are applications really using? > > > > http://lwn.net/Articles/230975/ > > > > > > > > Another helpful patch could be: > > > > maps: PSS(proportional set size) accounting in smaps > > > > http://lkml.org/lkml/2007/8/19/23 > > > > > > Thanks a lot, very useful pages indeed. > > > > > > However they still don't explain how I can avoid counting memory > > > twice for /proc/PID1 and /proc/PID2 when PID2 is a child of PID1, > > > created with CLONE_VM. > > > > > > The example: I allocate 1234k, dirty it, then clone with CLONE_VM. > > > I will seemingly have two processes, each using 1234k, _privately_ > > > (i.e., pages are not shown as shared in smaps) - > > > which is technically correct, pages are not shared with other VMs, > > > but they ARE shared by means of these two processes having the same VM! > > > > > > How userspace tools can figure out that these processes have shared VM? > > > > > > IOW: do we need "VMsharecount: N" in addition to "Threads: N" > > > in /proc/PID/status? > > > > A full solution would require two parameters, i.e. VmUsers/VmMagic. > > > > But please make sure the new lines won't break important tools like > > ps/top/pmaps/... > > Should be safe - tools skip lines they do not recognize.
Except yours ;-)
FYI, I found another tool that depends on status: atop.
> Ok, we have "Threads: N". > > I can cook up a patch which adds count of processes > which share VM with us - it's just atomic_read(¤t->mm->mm_users).
Yeah, the code itself would be simple.
> What name do you like? > > SharedVmCount: N > VmUsers: N > other?
I'd prefer VmUsers: that's the choice of source code.
Fengguang
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