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SubjectRe: [RFC][PATCH] Add file RSS accounting to the memory resource controller
* KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> [2009-04-15 09:01:30]:

> I think your concept is good. A few comments below.
>

Thanks,

> On Tue, 14 Apr 2009 23:37:06 +0530
> Balbir Singh <balbir@linux.vnet.ibm.com> wrote:
>
> >
> > Feature: Add file RSS tracking per memory cgroup
> >
> > From: Balbir Singh <balbir@linux.vnet.ibm.com>
> >
> > Testing
> >
> > 1. Feature enabled, built and booted the kernel. Mounted the memory
> > resource controller and verified the statistics
> > 2. Compiled with CGROUP_MEM_RES_CTLR disabled
> >
> > 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 "file_rss" data and hope to educate the end
> > user through documentation.
> > ---
> >
> > include/linux/memcontrol.h | 7 +++++++
> > include/linux/rmap.h | 4 ++--
> > mm/filemap_xip.c | 2 +-
> > mm/fremap.c | 2 +-
> > mm/memcontrol.c | 34 +++++++++++++++++++++++++++++++++-
> > mm/memory.c | 8 ++++----
> > mm/migrate.c | 2 +-
> > mm/rmap.c | 13 ++++++++-----
> > 8 files changed, 57 insertions(+), 15 deletions(-)
> >
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 18146c9..c844a13 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -116,6 +116,8 @@ static inline bool mem_cgroup_disabled(void)
> > }
> >
> > extern bool mem_cgroup_oom_called(struct task_struct *task);
> > +extern void
> > +mem_cgroup_update_statistics(struct page *page, struct mm_struct *mm, int val);
> >
> > #else /* CONFIG_CGROUP_MEM_RES_CTLR */
> > struct mem_cgroup;
> > @@ -264,6 +266,11 @@ mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> > {
> > }
> >
> > +static inline void
> > +mem_cgroup_update_statistics(struct page *page, struct mm_struct *mm, int val)
> > +{
> > +}
> > +
> > #endif /* CONFIG_CGROUP_MEM_CONT */
> >
> > #endif /* _LINUX_MEMCONTROL_H */
> > diff --git a/include/linux/rmap.h b/include/linux/rmap.h
> > index b35bc0e..01b4af1 100644
> > --- a/include/linux/rmap.h
> > +++ b/include/linux/rmap.h
> > @@ -68,8 +68,8 @@ void __anon_vma_link(struct vm_area_struct *);
> > */
> > void page_add_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
> > void page_add_new_anon_rmap(struct page *, struct vm_area_struct *, unsigned long);
> > -void page_add_file_rmap(struct page *);
> > -void page_remove_rmap(struct page *);
> > +void page_add_file_rmap(struct page *, struct vm_area_struct *);
> > +void page_remove_rmap(struct page *, struct vm_area_struct *);
> >
> > #ifdef CONFIG_DEBUG_VM
> > void page_dup_rmap(struct page *page, struct vm_area_struct *vma, unsigned long address);
> > diff --git a/mm/filemap_xip.c b/mm/filemap_xip.c
> > index 427dfe3..e8b2b18 100644
> > --- a/mm/filemap_xip.c
> > +++ b/mm/filemap_xip.c
> > @@ -193,7 +193,7 @@ retry:
> > /* Nuke the page table entry. */
> > flush_cache_page(vma, address, pte_pfn(*pte));
> > pteval = ptep_clear_flush_notify(vma, address, pte);
> > - page_remove_rmap(page);
> > + page_remove_rmap(page, vma);
> > dec_mm_counter(mm, file_rss);
> > BUG_ON(pte_dirty(pteval));
> > pte_unmap_unlock(pte, ptl);
> > diff --git a/mm/fremap.c b/mm/fremap.c
> > index b6ec85a..01ea2da 100644
> > --- a/mm/fremap.c
> > +++ b/mm/fremap.c
> > @@ -37,7 +37,7 @@ static void zap_pte(struct mm_struct *mm, struct vm_area_struct *vma,
> > if (page) {
> > if (pte_dirty(pte))
> > set_page_dirty(page);
> > - page_remove_rmap(page);
> > + page_remove_rmap(page, vma);
> > page_cache_release(page);
> > update_hiwater_rss(mm);
> > dec_mm_counter(mm, file_rss);
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index e44fb0f..d903b61 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -62,7 +62,8 @@ enum mem_cgroup_stat_index {
> > * For MEM_CONTAINER_TYPE_ALL, usage = pagecache + rss.
> > */
> > MEM_CGROUP_STAT_CACHE, /* # of pages charged as cache */
> > - MEM_CGROUP_STAT_RSS, /* # of pages charged as rss */
> > + MEM_CGROUP_STAT_RSS, /* # of pages charged as anon rss */
> > + MEM_CGROUP_STAT_FILE_RSS, /* # of pages charged as file rss */
>
> I don't like the word "FILE RSS". MAPPED FILE PAGES or some will be more straigtforward.
> (IIUC, meminfo shows this information as MAPPED_FILE)

OK, I'll call it mapped_file

>
> > MEM_CGROUP_STAT_PGPGIN_COUNT, /* # of pages paged in */
> > MEM_CGROUP_STAT_PGPGOUT_COUNT, /* # of pages paged out */
> >
> > @@ -321,6 +322,33 @@ static bool mem_cgroup_is_obsolete(struct mem_cgroup *mem)
> > return css_is_removed(&mem->css);
> > }
> >
> > +/*
> > + * Currently used to update file_rss statistics, but the routine can be
> > + * generalized to update other statistics as well.
> > + */
> > +void
> > +mem_cgroup_update_statistics(struct page *page, struct mm_struct *mm, int val)
> > +{
>
> Hmm. "mem_cgroup_update_statistics()" have wider meaning than what it does..
> Could you
> - modify function name for showing "this function counts MAPPED_FILE"

I thought about this, but made it more generic. How about
mem_cgroup_update_mapped_file_stat()

> or
> - add a function argument as "Which counter should be modified."
>
>
> > + struct mem_cgroup *mem;
> > + struct mem_cgroup_stat *stat;
> > + struct mem_cgroup_stat_cpu *cpustat;
> > + 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_FILE_RSS, val);
> > +}
> >
> > /*
> > * Call callback function against all cgroup under hierarchy tree.
> > @@ -2051,6 +2079,7 @@ static int mem_cgroup_reset(struct cgroup *cont, unsigned int event)
> > enum {
> > MCS_CACHE,
> > MCS_RSS,
> > + MCS_FILE_RSS,
> > MCS_PGPGIN,
> > MCS_PGPGOUT,
> > MCS_INACTIVE_ANON,
> > @@ -2071,6 +2100,7 @@ struct {
> > } memcg_stat_strings[NR_MCS_STAT] = {
> > {"cache", "total_cache"},
> > {"rss", "total_rss"},
> > + {"file_rss", "total_file_rss"},
> > {"pgpgin", "total_pgpgin"},
> > {"pgpgout", "total_pgpgout"},
> > {"inactive_anon", "total_inactive_anon"},
> > @@ -2091,6 +2121,8 @@ static int mem_cgroup_get_local_stat(struct mem_cgroup *mem, void *data)
> > s->stat[MCS_CACHE] += val * PAGE_SIZE;
> > val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_RSS);
> > s->stat[MCS_RSS] += val * PAGE_SIZE;
> > + val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_FILE_RSS);
> > + s->stat[MCS_FILE_RSS] += val * PAGE_SIZE;
> > val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_PGPGIN_COUNT);
> > s->stat[MCS_PGPGIN] += val;
> > val = mem_cgroup_read_stat(&mem->stat, MEM_CGROUP_STAT_PGPGOUT_COUNT);
>
> IIUC, you have to add hook to force_empty() and move FILE_RSS counter to the parent.
> I hope there is no terrible race around force empty...
>
> Thanks,
> -Kame
>

Good catch, I'll do the necessary changes in
mem_cgroup_move_account(). I don't see any dirty race occuring, since
the counters are per-cpu. I'll double check however.
--
Balbir


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