linux-kernel - Re: [PATCH 5/7] Fix not good check of mem_cgroup_local

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Message-ID: <BANLkTi=4o-xY46OtsvNCxVKUT-qJBXRMMFZCe-m7eMV-_mesXw@mail.gmail.com>
Date:	Fri, 17 Jun 2011 15:27:36 -0700
From:	Ying Han <yinghan@...gle.com>
To:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc:	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
	"bsingharora@...il.com" <bsingharora@...il.com>,
	Michal Hocko <mhocko@...e.cz>,
	"hannes@...xchg.org" <hannes@...xchg.org>
Subject: Re: [PATCH 5/7] Fix not good check of mem_cgroup_local_usage()

On Wed, Jun 15, 2011 at 8:54 PM, KAMEZAWA Hiroyuki
<kamezawa.hiroyu@...fujitsu.com> wrote:
> From fcfc6ee9847b0b2571cd6e9847572d7c70e1e2b2 Mon Sep 17 00:00:00 2001
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> Date: Thu, 16 Jun 2011 09:23:54 +0900
> Subject: [PATCH 5/7] Fix not good check of mem_cgroup_local_usage()
>
> Now, mem_cgroup_local_usage(memcg) is used as hint for scanning memory
> cgroup hierarchy. If it returns true, the memcg has some reclaimable memory.
>
> But this function doesn't take care of
>  - unevictable pages
>  - anon pages on swapless system.
>
> This patch fixes the function to use LRU information.
> For NUMA, for avoid scanning, numa scan bitmap is used. If it's
> empty, some more precise check will be done.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
> ---
>  mm/memcontrol.c |   43 +++++++++++++++++++++++++++++++++----------
>  1 files changed, 33 insertions(+), 10 deletions(-)
>
> Index: mmotm-0615/mm/memcontrol.c
> ===================================================================
> --- mmotm-0615.orig/mm/memcontrol.c
> +++ mmotm-0615/mm/memcontrol.c
> @@ -632,15 +632,6 @@ static long mem_cgroup_read_stat(struct
>        return val;
>  }
>
> -static long mem_cgroup_local_usage(struct mem_cgroup *mem)
> -{
> -       long ret;
> -
> -       ret = mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_RSS);
> -       ret += mem_cgroup_read_stat(mem, MEM_CGROUP_STAT_CACHE);
> -       return ret;
> -}
> -
>  static void mem_cgroup_swap_statistics(struct mem_cgroup *mem,
>                                         bool charge)
>  {
> @@ -1713,6 +1704,23 @@ static void mem_cgroup_numascan_init(str
>        mutex_init(&mem->numascan_mutex);
>  }
>
> +static bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
> +{
> +       if (!nodes_empty(mem->scan_nodes))
> +               return true;
> +       /* slow path */
> +       if (mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_FILE))
> +               return true;
> +       if (mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_FILE))
> +               return true;

Wondering if we can simplify this like:

if (mem_cgroup_nr_file_lru_pages(mem))
   return true;


> +       if (noswap || !total_swap_pages)
> +               return false;
> +       if (mem_cgroup_get_local_zonestat(mem, LRU_INACTIVE_ANON))
> +               return true;
> +       if (mem_cgroup_get_local_zonestat(mem, LRU_ACTIVE_ANON))
> +               return true;

the same:
if (mem_cgroup_nr_anon_lru_pages(mem))
   return true;

> +       return false;
> +}

The two functions above are part of memory.numa_stat patch which is in
mmotm i believe. Just feel the functionality a bit duplicate except
the noswap parameter and scan_nodes.

--Ying

>  #else
>  int mem_cgroup_select_victim_node(struct mem_cgroup *mem)
>  {
> @@ -1722,6 +1730,21 @@ static void mem_cgroup_numascan_init(str
>  {
>        return 0;
>  }
> +
> +static bool mem_cgroup_reclaimable(struct mem_cgroup *mem, bool noswap)
> +{
> +       if (mem_cgroup_get_zonestat_node(mem, 0, LRU_INACTIVE_FILE))
> +               return true;
> +       if (mem_cgroup_get_zonestat_node(mem, 0, LRU_ACTIVE_FILE))
> +               return true;
> +       if (noswap || !total_swap_pages)
> +               return false;
> +       if (mem_cgroup_get_zonestat_node(mem, 0, LRU_INACTIVE_ANON))
> +               return true;
> +       if (mem_cgroup_get_zonestat_node(mem, 0, LRU_ACTIVE_ANON))
> +               return true;
> +       return false;
> +}
>  #endif
>
>
> @@ -1811,7 +1834,7 @@ again:
>
>        while (visit--) {
>                victim = mem_cgroup_select_victim(root_mem);
> -               if (!mem_cgroup_local_usage(victim)) {
> +               if (!mem_cgroup_reclaimable(victim, noswap)) {
>                        /* this cgroup's local usage == 0 */
>                        css_put(&victim->css);
>                        continue;
>
>
--
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