Messages in this thread | | | Date | Tue, 7 Apr 2009 15:40:45 +0530 | From | Balbir Singh <> | Subject | Re: [RFI] Shared accounting for memory resource controller |
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* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-07 17:24:19]:
> On Tue, 7 Apr 2009 13:33:55 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-07 16:33:31]: > > > > > On Tue, 7 Apr 2009 12:48:25 +0530 > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-07 16:00:14]: > > > > > > > > > On Tue, 7 Apr 2009 12:07:22 +0530 > > > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > > > > > > > Hi, All, > > > > > > > > > > > > This is a request for input for the design of shared page accounting for > > > > > > the memory resource controller, here is what I have so far > > > > > > > > > > > > > > > > In my first impression, I think simple counting is impossible. > > > > > IOW, "usage count" and "shared or not" is very different problem. > > > > > > > > > > Assume a page and its page_cgroup. > > > > > > > > > > Case 1) > > > > > 1. a page is mapped by process-X under group-A > > > > > 2. its mapped by process-Y in group-B (now, shared and charged under group-A) > > > > > 3. move process-X to group-B > > > > > 4. now the page is not shared. > > > > > > > > > > > > > By shared I don't mean only between cgroups, it could be a page shared > > > > in the same cgroup > > > > > > > Hmm, is it good information ? > > > > > > Such kind of information can be calucated by > > > == > > > rss = 0; > > > for_each_process_under_cgroup() { > > > mm = tsk->mm > > > rss += mm->anon_rss; > > > } > > > some_of_all_rss = rss; > > > > > > shared_ratio = mem_cgrou->rss *100 / some_of_all_rss. > > > == > > > if 100%, all anon memory are not shared. > > > > > > > Why only anon? > > no serious intention. > Just because you wrote "expect the user to account all cached pages as shared" ;)
OK, I think we should mention that we can treat unmapped cache as shared :)
> > > This seems like a good idea, except when we have a page > > charged to a cgroup and the task that charged it has migrated, in that > > case sum_of_all_rss will be 0. > > > Yes. But we don't move pages at task-move under expectation that moved > process will call fork() soon. > "task move" has its own problem, so ignoring it for now is a choice. > That kind of troubls can be treated when we fixes "task move". > (or fix "task move" first.) >
Yes, but the point I was making was that we could have pages left over without tasks remaining, in the case of shared pages. I think we can handle them suitably, probably an implementation issue.
-- Balbir
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