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    SubjectRe: Re: [PATCH 3/4] memcg: avoid account not-on-LRU pages
    ----- Original Message -----
    >On Mon, 29 Sep 2008 19:23:39 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fuj
    itsu.com> wrote:
    >> There are not-on-LRU pages which can be mapped and they are not worth to
    >> be accounted. (becasue we can't shrink them and need dirty codes to handle
    >> specical case) We'd like to make use of usual objrmap/radix-tree's protcol
    >> and don't want to account out-of-vm's control pages.
    >>
    >> When special_mapping_fault() is called, page->mapping is tend to be NULL
    >> and it's charged as Anonymous page.
    >> insert_page() also handles some special pages from drivers.
    >>
    >> This patch is for avoiding to account special pages.
    >>
    >> Changlog: v5 -> v6
    >> - modified Documentation.
    >> - fixed to charge only when a page is newly allocated.
    >>
    >> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    >>
    >> Documentation/controllers/memory.txt | 24 ++++++++++++++++--------
    >> mm/memory.c | 29 +++++++++++++----------------
    >> mm/rmap.c | 4 ++--
    >> 3 files changed, 31 insertions(+), 26 deletions(-)
    >>
    >> Index: mmotm-2.6.27-rc7+/mm/memory.c
    >> ===================================================================
    >> --- mmotm-2.6.27-rc7+.orig/mm/memory.c
    >> +++ mmotm-2.6.27-rc7+/mm/memory.c
    >> @@ -1323,18 +1323,14 @@ static int insert_page(struct vm_area_st
    >> pte_t *pte;
    >> spinlock_t *ptl;
    >>
    >> - retval = mem_cgroup_charge(page, mm, GFP_KERNEL);
    >> - if (retval)
    >> - goto out;
    >> -
    >> retval = -EINVAL;
    >> if (PageAnon(page))
    >> - goto out_uncharge;
    >> + goto out;
    >> retval = -ENOMEM;
    >> flush_dcache_page(page);
    >> pte = get_locked_pte(mm, addr, &ptl);
    >> if (!pte)
    >> - goto out_uncharge;
    >> + goto out;
    >> retval = -EBUSY;
    >> if (!pte_none(*pte))
    >> goto out_unlock;
    >> @@ -1350,8 +1346,6 @@ static int insert_page(struct vm_area_st
    >> return retval;
    >> out_unlock:
    >> pte_unmap_unlock(pte, ptl);
    >> -out_uncharge:
    >> - mem_cgroup_uncharge_page(page);
    >> out:
    >> return retval;
    >> }
    >> @@ -2463,6 +2457,7 @@ static int __do_fault(struct mm_struct *
    >> struct page *page;
    >> pte_t entry;
    >> int anon = 0;
    >> + int charged = 0;
    >> struct page *dirty_page = NULL;
    >> struct vm_fault vmf;
    >> int ret;
    >> @@ -2503,6 +2498,12 @@ static int __do_fault(struct mm_struct *
    >> ret = VM_FAULT_OOM;
    >> goto out;
    >> }
    >> + if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
    >> + ret = VM_FAULT_OOM;
    >> + page_cache_release(page);
    >> + goto out;
    >> + }
    >> + charged = 1;
    >> /*
    >> * Don't let another task, with possibly unlocked vma,
    >> * keep the mlocked page.
    >> @@ -2543,11 +2544,6 @@ static int __do_fault(struct mm_struct *
    >>
    >> }
    >>
    >> - if (mem_cgroup_charge(page, mm, GFP_KERNEL)) {
    >> - ret = VM_FAULT_OOM;
    >> - goto out;
    >> - }
    >> -
    >> page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
    >>
    >> /*
    >> @@ -2585,10 +2581,11 @@ static int __do_fault(struct mm_struct *
    >> /* no need to invalidate: a not-present page won't be cached */
    >> update_mmu_cache(vma, address, entry);
    >> } else {
    >> - mem_cgroup_uncharge_page(page);
    >> - if (anon)
    >> + if (charged)
    >> + mem_cgroup_uncharge_page(page);
    >> + if (anon) {
    >> page_cache_release(page);
    >> - else
    >> + } else
    >> anon = 1; /* no anon but release faulted_page */
    >> }
    >>
    >
    >checkpatch reports a warning here.
    >
    >I think it should be like
    >
    Oh, thanks. I'll post fixed one, tomorrow.

    Thanks,
    -Kame

    >@@ -2585,7 +2581,8 @@ static int __do_fault(struct mm_struct *mm, struct vm_a
    rea_struct *vma,
    > /* no need to invalidate: a not-present page won't be cached */
    > update_mmu_cache(vma, address, entry);
    > } else {
    >- mem_cgroup_uncharge_page(page);
    >+ if (charged)
    >+ mem_cgroup_uncharge_page(page);
    > if (anon)
    > page_cache_release(page);
    > else
    >
    >
    >Thanks,
    >Daisuke Nishimura.
    >
    >> Index: mmotm-2.6.27-rc7+/mm/rmap.c
    >> ===================================================================
    >> --- mmotm-2.6.27-rc7+.orig/mm/rmap.c
    >> +++ mmotm-2.6.27-rc7+/mm/rmap.c
    >> @@ -725,8 +725,8 @@ void page_remove_rmap(struct page *page,
    >> page_clear_dirty(page);
    >> set_page_dirty(page);
    >> }
    >> -
    >> - mem_cgroup_uncharge_page(page);
    >> + if (PageAnon(page))
    >> + mem_cgroup_uncharge_page(page);
    >> __dec_zone_page_state(page,
    >> PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
    >> /*
    >> Index: mmotm-2.6.27-rc7+/Documentation/controllers/memory.txt
    >> ===================================================================
    >> --- mmotm-2.6.27-rc7+.orig/Documentation/controllers/memory.txt
    >> +++ mmotm-2.6.27-rc7+/Documentation/controllers/memory.txt
    >> @@ -112,14 +112,22 @@ the per cgroup LRU.
    >>
    >> 2.2.1 Accounting details
    >>
    >> -All mapped pages (RSS) and unmapped user pages (Page Cache) are accounted.
    >> -RSS pages are accounted at the time of page_add_*_rmap() unless they've al
    ready
    >> -been accounted for earlier. A file page will be accounted for as Page Cach
    e;
    >> -it's mapped into the page tables of a process, duplicate accounting is car
    efully
    >> -avoided. Page Cache pages are accounted at the time of add_to_page_cache()
    .
    >> -The corresponding routines that remove a page from the page tables or remo
    ves
    >> -a page from Page Cache is used to decrement the accounting counters of the
    >> -cgroup.
    >> +All mapped anon pages (RSS) and cache pages (Page Cache) are accounted.
    >> +(some pages which never be reclaimable and will not be on global LRU
    >> + are not accounted. we just accounts pages under usual vm management.)
    >> +
    >> +RSS pages are accounted at page_fault unless they've already been accounte
    d
    >> +for earlier. A file page will be accounted for as Page Cache when it's
    >> +inserted into inode (radix-tree). While it's mapped into the page tables o
    f
    >> +processes, duplicate accounting is carefully avoided.
    >> +
    >> +A RSS page is unaccounted when it's fully unmapped. A PageCache page is
    >> +unaccounted when it's removed from radix-tree.
    >> +
    >> +At page migration, accounting information is kept.
    >> +
    >> +Note: we just account pages-on-lru because our purpose is to control amoun
    t
    >> +of used pages. not-on-lru pages are tend to be out-of-control from vm view
    .
    >>
    >> 2.3 Shared Page Accounting
    >>
    >>



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