Messages in this thread |  | | | Date | Fri, 17 Apr 2009 12:49:51 +0900 | | From | KAMEZAWA Hiroyuki <> | | Subject | Re: [PATCH] Add file based RSS accounting for memory resource controller (v2) |
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On Fri, 17 Apr 2009 09:15:39 +0530 Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
> * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-17 11:03:50]: > > > On Fri, 17 Apr 2009 07:10:42 +0530 > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-17 09:14:59]: > > > > > > > On Thu, 16 Apr 2009 17:33:16 +0530 > > > > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > > > > > * KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-16 17:15:35]: > > > > > > > > > > > > > > > > > > Sorry, some troubles found. Ignore above Ack. 3points now. > > > > > > > > > > > > > > 1. get_cpu should be after (*) > > > > > > > ==mem_cgroup_update_mapped_file_stat() > > > > > > > + int cpu = get_cpu(); > > > > > > > + > > > > > > > + if (!page_is_file_cache(page)) > > > > > > > + return; > > > > > > > + > > > > > > > + if (unlikely(!mm)) > > > > > > > + mm = &init_mm; > > > > > > > + > > > > > > > + mem = try_get_mem_cgroup_from_mm(mm); > > > > > > > + if (!mem) > > > > > > > + return; > > > > > > > + ----------------------------------------(*) > > > > > > > + stat = &mem->stat; > > > > > > > + cpustat = &stat->cpustat[cpu]; > > > > > > > + > > > > > > > + __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_MAPPED_FILE, val); > > > > > > > + put_cpu(); > > > > > > > +} > > > > > > > == > > > > > > > > > > Yes or I should have a goto > > > > > > > > > > > > > > > > > > > 2. In above, "mem" shouldn't be got from "mm"....please get "mem" from page_cgroup. > > > > > > > (Because it's file cache, pc->mem_cgroup is not NULL always.) > > > > > > > > > > Hmmm.. not sure I understand this part. Are you suggesting that mm can > > > > > be NULL? > > > > No. > > > > > > > > > I added the check for !mm as a safety check. Since this > > > > > routine is only called from rmap context, mm is not NULL, hence mem > > > > > should not be NULL. Did you find a race between mm->owner assignment > > > > > and lookup via mm->owner? > > > > > > > > > No. > > > > > > > > page_cgroup->mem_cgroup != try_get_mem_cgroup_from_mm(mm); in many many cases. > > > > > > > > For example, libc and /bin/*** is tend to be loaded into default cgroup at boot but > > > > used by many cgroups. But mapcount of page caches for /bin/*** is 0 if not running. > > > > > > > > Then, File_Mapped can be greater than Cached easily if you use mm->owner. > > > > > > > > I can't estimate RSS in *my* cgroup if File_Mapped includes pages which is under > > > > other cgroups. It's meaningless. > > > > Especially, when Cached==0 but File_Mapped > 0, I think "oh, the kernel leaks somehing..hmm..." > > > > > > > > By useing page_cgroup->mem_cgroup, we can avoid above mess. > > > > > > Yes, I see your point. I wanted mapped_file to show up in the cgroup > > > that mapped the page. But this works for me as well, but that means > > > we'll nest the page cgroup lock under the PTE lock. > > > > Don't worry. we do that nest at ANON's uncharge(), already. > > > > About cost: > > > > IIUC, the number of "mapcount 0->1/1->0" of file caches are much smaller than > > that of o Anon. And there will be not very much cache pingpong. > > > > If you use PCG_MAPPED flag in page_cgroup (as my patch), you can use > > not-atomic version of set/clear when update is only under lock_page_cgroup(). > > If you find better way, plz use it. But we can't avoid some kind of atomic ops > > for correct accounting, I think. > > > > Can you sign off on your patch, so that I can take it with your > signed-off-by. I will also make some minor changes, get_cpu() is not > needed, since we are in preempt disable context. > Hmm, Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
But some more clean up is necesarry.
=== This part == + lock_page_cgroup(pc); + mem = pc->mem_cgroup; + if (mem) { + cpu = get_cpu(); + stat = &mem->stat; + cpustat = &stat->cpustat[cpu]; + if (map) === Should be == + lock_page_cgroup(pc); if (!PageCgroupUsed(pc)) { unlock_page_cgroup(pc); return; } mem = pc->mem_cgroup VM_BUG_ON(!mem); cpu = get_cpu(); stat = &mem->stat; cpustat = &stat->cpustat[cpu]; if (map) ..... Maybe much cleaner.
Thanks, -Kame
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