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    Subject[PATCH v3] memcg: remove PCG_CACHE page_cgroup flag
    I think this version is much simplified.

    ==
    From 5700a4fe9c581e1ebaa021ba6119dc8d921b024f Mon Sep 17 00:00:00 2001
    From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    Date: Thu, 19 Jan 2012 17:09:41 +0900
    Subject: [PATCH v3] memcg: remove PCG_CACHE

    We record 'the page is cache' by PCG_CACHE bit to page_cgroup.
    Here, "CACHE" means anonymous user pages (and SwapCache). This
    doesn't include shmem.

    Consdering callers, at charge/uncharge, the caller should know
    what the page is and we don't need to record it by using 1bit
    per page.

    This patch removes PCG_CACHE bit and make callers of
    mem_cgroup_charge_statistics() to specify what the page is.

    Changelog since v2
    - removed 'not_rss', added 'anon'
    - changed a meaning of arguments to mem_cgroup_charge_statisitcs()
    - removed a patch to mem_cgroup_uncharge_cache
    - simplified comment.

    Changelog since RFC.
    - rebased onto memcg-devel
    - rename 'file' to 'not_rss'
    - some cleanup and added comment.

    Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    ---
    include/linux/page_cgroup.h | 8 +------
    mm/memcontrol.c | 48 +++++++++++++++++++++++-------------------
    2 files changed, 27 insertions(+), 29 deletions(-)

    diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
    index a2d1177..1060292 100644
    --- a/include/linux/page_cgroup.h
    +++ b/include/linux/page_cgroup.h
    @@ -4,7 +4,6 @@
    enum {
    /* flags for mem_cgroup */
    PCG_LOCK, /* Lock for pc->mem_cgroup and following bits. */
    - PCG_CACHE, /* charged as cache */
    PCG_USED, /* this object is in use. */
    PCG_MIGRATION, /* under page migration */
    /* flags for mem_cgroup and file and I/O status */
    @@ -64,11 +63,6 @@ static inline void ClearPageCgroup##uname(struct page_cgroup *pc) \
    static inline int TestClearPageCgroup##uname(struct page_cgroup *pc) \
    { return test_and_clear_bit(PCG_##lname, &pc->flags); }

    -/* Cache flag is set only once (at allocation) */
    -TESTPCGFLAG(Cache, CACHE)
    -CLEARPCGFLAG(Cache, CACHE)
    -SETPCGFLAG(Cache, CACHE)
    -
    TESTPCGFLAG(Used, USED)
    CLEARPCGFLAG(Used, USED)
    SETPCGFLAG(Used, USED)
    @@ -85,7 +79,7 @@ static inline void lock_page_cgroup(struct page_cgroup *pc)
    {
    /*
    * Don't take this lock in IRQ context.
    - * This lock is for pc->mem_cgroup, USED, CACHE, MIGRATION
    + * This lock is for pc->mem_cgroup, USED, MIGRATION
    */
    bit_spin_lock(PCG_LOCK, &pc->flags);
    }
    diff --git a/mm/memcontrol.c b/mm/memcontrol.c
    index ff24520..f000c82 100644
    --- a/mm/memcontrol.c
    +++ b/mm/memcontrol.c
    @@ -672,15 +672,19 @@ static unsigned long mem_cgroup_read_events(struct mem_cgroup *memcg,
    }

    static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
    - bool file, int nr_pages)
    + bool rss, int nr_pages)
    {
    preempt_disable();

    - if (file)
    - __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
    + /*
    + * Here, RSS means 'mapped anon' and anon's SwapCache. Shmem/tmpfs is
    + * counted as CACHE even if it's on ANON LRU.
    + */
    + if (rss)
    + __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
    nr_pages);
    else
    - __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_RSS],
    + __this_cpu_add(memcg->stat->count[MEM_CGROUP_STAT_CACHE],
    nr_pages);

    /* pagein of a big page is an event. So, ignore page size */
    @@ -2409,6 +2413,8 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
    struct page_cgroup *pc,
    enum charge_type ctype)
    {
    + bool anon;
    +
    lock_page_cgroup(pc);
    if (unlikely(PageCgroupUsed(pc))) {
    unlock_page_cgroup(pc);
    @@ -2428,21 +2434,14 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg,
    * See mem_cgroup_add_lru_list(), etc.
    */
    smp_wmb();
    - switch (ctype) {
    - case MEM_CGROUP_CHARGE_TYPE_CACHE:
    - case MEM_CGROUP_CHARGE_TYPE_SHMEM:
    - SetPageCgroupCache(pc);
    - SetPageCgroupUsed(pc);
    - break;
    - case MEM_CGROUP_CHARGE_TYPE_MAPPED:
    - ClearPageCgroupCache(pc);
    - SetPageCgroupUsed(pc);
    - break;
    - default:
    - break;
    - }

    - mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), nr_pages);
    + SetPageCgroupUsed(pc);
    + if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED)
    + anon = true;
    + else
    + anon = false;
    +
    + mem_cgroup_charge_statistics(memcg, anon, nr_pages);
    unlock_page_cgroup(pc);
    WARN_ON_ONCE(PageLRU(page));
    /*
    @@ -2507,6 +2506,7 @@ static int mem_cgroup_move_account(struct page *page,
    {
    unsigned long flags;
    int ret;
    + bool anon = PageAnon(page);

    VM_BUG_ON(from == to);
    VM_BUG_ON(PageLRU(page));
    @@ -2535,14 +2535,14 @@ static int mem_cgroup_move_account(struct page *page,
    __this_cpu_inc(to->stat->count[MEM_CGROUP_STAT_FILE_MAPPED]);
    preempt_enable();
    }
    - mem_cgroup_charge_statistics(from, PageCgroupCache(pc), -nr_pages);
    + mem_cgroup_charge_statistics(from, anon, -nr_pages);
    if (uncharge)
    /* This is not "cancel", but cancel_charge does all we need. */
    __mem_cgroup_cancel_charge(from, nr_pages);

    /* caller should have done css_get */
    pc->mem_cgroup = to;
    - mem_cgroup_charge_statistics(to, PageCgroupCache(pc), nr_pages);
    + mem_cgroup_charge_statistics(to, anon, nr_pages);
    /*
    * We charges against "to" which may not have any tasks. Then, "to"
    * can be under rmdir(). But in current implementation, caller of
    @@ -2890,6 +2890,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
    struct mem_cgroup *memcg = NULL;
    unsigned int nr_pages = 1;
    struct page_cgroup *pc;
    + bool anon;

    if (mem_cgroup_disabled())
    return NULL;
    @@ -2921,6 +2922,7 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
    /* See mem_cgroup_prepare_migration() */
    if (page_mapped(page) || PageCgroupMigration(pc))
    goto unlock_out;
    + anon = true;
    break;
    case MEM_CGROUP_CHARGE_TYPE_SWAPOUT:
    if (!PageAnon(page)) { /* Shared memory */
    @@ -2928,12 +2930,14 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype)
    goto unlock_out;
    } else if (page_mapped(page)) /* Anon */
    goto unlock_out;
    + anon = true;
    break;
    default:
    + anon = false;
    break;
    }

    - mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -nr_pages);
    + mem_cgroup_charge_statistics(memcg, anon, -nr_pages);

    ClearPageCgroupUsed(pc);
    /*
    @@ -3319,7 +3323,7 @@ void mem_cgroup_replace_page_cache(struct page *oldpage,
    /* fix accounting on old pages */
    lock_page_cgroup(pc);
    memcg = pc->mem_cgroup;
    - mem_cgroup_charge_statistics(memcg, PageCgroupCache(pc), -1);
    + mem_cgroup_charge_statistics(memcg, false, -1);
    ClearPageCgroupUsed(pc);
    unlock_page_cgroup(pc);

    --
    1.7.4.1



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