Messages in this thread | | | Date | Wed, 8 Apr 2009 17:54:09 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [RFI] Shared accounting for memory resource controller |
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On Wed, 8 Apr 2009 14:19:52 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-08 17:03:41]: > > > On Wed, 8 Apr 2009 13:18:09 +0530 > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > > > 3. Using the above, we can then try to (using an algorithm you > > > > > proposed), try to do some work for figuring out the shared percentage. > > > > > > > > > This is the point. At last. Why "# of shared pages" is important ? > > > > > > > > > > I posted this in my motivation yesterday. # of shared pages can help > > > plan the system better and the size of the cgroup. A cgroup might have > > > small usage_in_bytes but large number of shared pages. We need a > > > metric that can help figure out the fair usage of the cgroup. > > > > > I don't fully understand but NR_FILE_MAPPED is an information in /proc/meminfo. > > I personally think I want to support information in /proc/meminfo per memcg. > > > > Hmm ? then, if you add a hook, it seems > > == mm/rmap.c > > 689 void page_add_file_rmap(struct page *page) > > 690 { > > 691 if (atomic_inc_and_test(&page->_mapcount)) > > 692 __inc_zone_page_state(page, NR_FILE_MAPPED); > > 693 } > > == page_remove_rmap(struct page *page) > > 739 __dec_zone_page_state(page, > > 740 PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED); > > == > > > > Is good place to go, maybe. > > > > page->page_cgroup->mem_cgroup-> inc/dec counter ? > > > > Maybe the patch itself will be simple, overhead is unknown.. > > I thought of the same thing, but then moved to the following > > ... mem_cgroup_charge_statistics(..) { > if (page_mapcount(page) == 0 && page_is_file_cache(page)) > __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_FILE_RSS, val); > > But I've not yet tested the end result > I think - at uncharge: charge_statistics is only called when FILE CACHE is removed from radix-tree. mem_cgroup_uncharge() is called only when PageAnon(page). - at charge: charge_statistics is only called when FILE CACHE is added to radix-tree.
This "checking only radix-tree insert/delete" help us to remove most of overheads on FILE CACHE.
So, adding new hooks to page_add_file_rmap() and page_remove_rmap() is a way to go. (and easy to understand because we account it at the same time NR_FILE_MAPPED is modified.)
Thanks, -Kame
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