Re: [PATCH v5 2/4] memcg: move memcg reclaimable page into tail of inactive list

[Minchan Kim <minchan.kim@gmail.com>]

Hi Kame,

On Fri, Feb 18, 2011 at 1:04 AM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@jp.fujitsu.com> wrote:
> On Fri, 18 Feb 2011 00:08:20 +0900
> Minchan Kim <minchan.kim@gmail.com> wrote:
>
>> The rotate_reclaimable_page function moves just written out
>> pages, which the VM wanted to reclaim, to the end of the
>> inactive list.  That way the VM will find those pages first
>> next time it needs to free memory.
>> This patch apply the rule in memcg.
>> It can help to prevent unnecessary working page eviction of memcg.
>>
>> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
>> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>> Reviewed-by: Rik van Riel <riel@redhat.com>
>> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
>> Cc: Johannes Weiner <hannes@cmpxchg.org>
>> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
>> ---
>> Changelog since v4:
>>  - add acked-by and reviewed-by
>>  - change description - suggested by Rik
>>
>>  include/linux/memcontrol.h |    6 ++++++
>>  mm/memcontrol.c            |   27 +++++++++++++++++++++++++++
>>  mm/swap.c                  |    3 ++-
>>  3 files changed, 35 insertions(+), 1 deletions(-)
>>
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index 3da48ae..5a5ce70 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -62,6 +62,7 @@ extern int mem_cgroup_cache_charge(struct page *page, struct mm_struct *mm,
>>                                       gfp_t gfp_mask);
>>  extern void mem_cgroup_add_lru_list(struct page *page, enum lru_list lru);
>>  extern void mem_cgroup_del_lru_list(struct page *page, enum lru_list lru);
>> +extern void mem_cgroup_rotate_reclaimable_page(struct page *page);
>>  extern void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru);
>>  extern void mem_cgroup_del_lru(struct page *page);
>>  extern void mem_cgroup_move_lists(struct page *page,
>> @@ -215,6 +216,11 @@ static inline void mem_cgroup_del_lru_list(struct page *page, int lru)
>>       return ;
>>  }
>>
>> +static inline inline void mem_cgroup_rotate_reclaimable_page(struct page *page)
>> +{
>> +     return ;
>> +}
>> +
>>  static inline void mem_cgroup_rotate_lru_list(struct page *page, int lru)
>>  {
>>       return ;
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 686f1ce..ab8bdff 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -813,6 +813,33 @@ void mem_cgroup_del_lru(struct page *page)
>>       mem_cgroup_del_lru_list(page, page_lru(page));
>>  }
>>
>> +/*
>> + * Writeback is about to end against a page which has been marked for immediate
>> + * reclaim.  If it still appears to be reclaimable, move it to the tail of the
>> + * inactive list.
>> + */
>> +void mem_cgroup_rotate_reclaimable_page(struct page *page)
>> +{
>> +     struct mem_cgroup_per_zone *mz;
>> +     struct page_cgroup *pc;
>> +     enum lru_list lru = page_lru_base_type(page);
>> +
>> +     if (mem_cgroup_disabled())
>> +             return;
>> +
>> +     pc = lookup_page_cgroup(page);
>> +     /*
>> +      * Used bit is set without atomic ops but after smp_wmb().
>> +      * For making pc->mem_cgroup visible, insert smp_rmb() here.
>> +      */
>> +     smp_rmb();
>> +     /* unused or root page is not rotated. */
>> +     if (!PageCgroupUsed(pc) || mem_cgroup_is_root(pc->mem_cgroup))
>> +             return;
>> +     mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>> +     list_move_tail(&pc->lru, &mz->lists[lru]);
>> +}
>> +
>
> Hmm, I'm sorry I misunderstand this. IIUC, page_lru_base_type() always returns
> LRU_INACTIVE_XXX and this function may move page from active LRU to inactive LRU.
>
> Then, LRU counters for memcg should be updated.

Goal of mem_cgroup_rotate_reclaimable_page is same with rotate_reclaimable_page.
It means the page was already in inactive list.
Look at the check !PageActive(page).

But if you want to make the function generally(ie, support
active->inactive, too), I don't mind it. but if you want it, let's
make rotate_reclaimable_page to general function, too. but now any
user doesn't use it.

Thanks for the careful review.

>
> Could you replace after lookup like this ?
>
>     VM_BUG_ON(!PageCgroupAcctLRU(pc))  /* Implies this pages must be on some LRU */
>     if (!PageCgroupUsed(pc))
>           return;
>     /* Used bit check is not necessary, because there is a case Unused page
>        is lazily on LRU. We trust AcctLRU bit. */
>     mz = page_cgroup_zoneinfo(pc->mem_cgroup, page);
>     MEM_CGROUP_ZSTAT(mz, page_lru(page)) -= 1 << compound_order(page);
>     MEM_CGROUP_ZSTAT(mz, lru) += 1 << compound_order(page)
>     if (mem_cgroup_is_root(pc->mem_cgroup))
>           return;
>     list_move_tail(&pc->lru, &mz->lists[lru])
>
>
> Thanks,
> -Kame
>>  void mem_cgroup_rotate_lru_list(struct page *page, enum lru_list lru)
>>  {
>>       struct mem_cgroup_per_zone *mz;
>> diff --git a/mm/swap.c b/mm/swap.c
>> index 4aea806..1b9e4eb 100644
>> --- a/mm/swap.c
>> +++ b/mm/swap.c
>> @@ -200,8 +200,9 @@ static void pagevec_move_tail(struct pagevec *pvec)
>>                       spin_lock(&zone->lru_lock);
>>               }
>>               if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) {
>> -                     int lru = page_lru_base_type(page);
>> +                     enum lru_list lru = page_lru_base_type(page);
>>                       list_move_tail(&page->lru, &zone->lru[lru].list);
>> +                     mem_cgroup_rotate_reclaimable_page(page);
>>                       pgmoved++;
>>               }
>>       }
>> --
>> 1.7.1
>>
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>
>



-- 
Kind regards,
Minchan Kim

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