Messages in this thread | | | Date | Wed, 22 Apr 2009 09:02:18 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH] Add file based RSS accounting for memory resource controller (v3) |
| |
On Tue, 21 Apr 2009 13:25:51 -0700 Andrew Morton <akpm@linux-foundation.org> wrote:
> On Fri, 17 Apr 2009 19:48:38 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > > > > > ... > > > > We currently don't track file RSS, the RSS we report is actually anon RSS. > > All the file mapped pages, come in through the page cache and get accounted > > there. This patch adds support for accounting file RSS pages. It should > > > > 1. Help improve the metrics reported by the memory resource controller > > 2. Will form the basis for a future shared memory accounting heuristic > > that has been proposed by Kamezawa. > > > > Unfortunately, we cannot rename the existing "rss" keyword used in memory.stat > > to "anon_rss". We however, add "mapped_file" data and hope to educate the end > > user through documentation. > > > > Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com> > > > > ... > > > > @@ -1096,6 +1135,10 @@ static int mem_cgroup_move_account(struct page_cgroup *pc, > > struct mem_cgroup_per_zone *from_mz, *to_mz; > > int nid, zid; > > int ret = -EBUSY; > > + struct page *page; > > + int cpu; > > + struct mem_cgroup_stat *stat; > > + struct mem_cgroup_stat_cpu *cpustat; > > > > VM_BUG_ON(from == to); > > VM_BUG_ON(PageLRU(pc->page)); > > @@ -1116,6 +1159,23 @@ static int mem_cgroup_move_account(struct page_cgroup *pc, > > > > res_counter_uncharge(&from->res, PAGE_SIZE); > > mem_cgroup_charge_statistics(from, pc, false); > > + > > + page = pc->page; > > + if (page_is_file_cache(page) && page_mapped(page)) { > > + cpu = smp_processor_id(); > > + /* Update mapped_file data for mem_cgroup "from" */ > > + stat = &from->stat; > > + cpustat = &stat->cpustat[cpu]; > > + __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_MAPPED_FILE, > > + -1); > > + > > + /* Update mapped_file data for mem_cgroup "to" */ > > + stat = &to->stat; > > + cpustat = &stat->cpustat[cpu]; > > + __mem_cgroup_stat_add_safe(cpustat, MEM_CGROUP_STAT_MAPPED_FILE, > > + 1); > > + } > > This function (mem_cgroup_move_account()) does a trylock_page_cgroup() > and if that fails it will bale out, and the newly-added code will not > be executed. yes. and returns -EBUSY.
> > What are the implications of this? Does the missed accounting later get > performed somewhere, or does the error remain in place? > no error just -BUSY. the caller (now, only force_empty is the caller) will do retry.
> That trylock_page_cgroup() really sucks - trylocks usually do. Could > someone please raise a patch which completely documents the reasons for > its presence, and for any other uncommented/unobvious trylocks? > > Where appropriate, the comment should explain why the trylock isn't > simply a bug - why it is safe and correct to omit the operations which > we wished to perform. > > Thanks. > Hmm...maybe we can replace trylock with lock, here.
IIRC, this has been trylock because the old routine uses other locks (mem_cgroup' zone mz->lru_lock) before calling this. mz->lru_lock lock_page_cgroup() And there was other routine which calls lock_page_cgroup()->mz->lru_lock. lock_page_cgroup() -> mz->lru_lock.
So, I used trylock here. But now, the lock(mz->lru_lock) is removed. I should check this.
Thank you for pointing out.
Regards, -Kame
| |