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From: Kirill Tkhai <ktkhai@virtuozzo.com>
To: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: akpm@linux-foundation.org, shakeelb@google.com,
	viro@zeniv.linux.org.uk, hannes@cmpxchg.org, mhocko@kernel.org,
	tglx@linutronix.de, pombredanne@nexb.com,
	stummala@codeaurora.org, gregkh@linuxfoundation.org,
	sfr@canb.auug.org.au, guro@fb.com, mka@chromium.org,
	penguin-kernel@I-love.SAKURA.ne.jp, chris@chris-wilson.co.uk,
	longman@redhat.com, minchan@kernel.org, hillf.zj@alibaba-inc.com,
	ying.huang@intel.com, mgorman@techsingularity.net, jbacik@fb.com,
	linux@roeck-us.net, linux-kernel@vger.kernel.org,
	linux-mm@kvack.org, willy@infradead.org, lirongqing@baidu.com,
	aryabinin@virtuozzo.com
Subject: Re: [PATCH v2 04/12] mm: Assign memcg-aware shrinkers bitmap to memcg
Date: Tue, 24 Apr 2018 15:13:53 +0300	[thread overview]
Message-ID: <7ea19fc4-f8a0-bf3a-8786-9d77e88cd049@virtuozzo.com> (raw)
In-Reply-To: <20180424112844.626madzs4cwoz5gh@esperanza>

Let's discuss on code with changes after your commits to v2 to have them made visible.
v3 is on the way

Kirill

On 24.04.2018 14:28, Vladimir Davydov wrote:
> On Mon, Apr 23, 2018 at 01:54:50PM +0300, Kirill Tkhai wrote:
>>>> @@ -1200,6 +1206,8 @@ extern int memcg_nr_cache_ids;
>>>>  void memcg_get_cache_ids(void);
>>>>  void memcg_put_cache_ids(void);
>>>>  
>>>> +extern int shrinkers_max_nr;
>>>> +
>>>
>>> memcg_shrinker_id_max?
>>
>> memcg_shrinker_id_max sounds like an includive value, doesn't it?
>> While shrinker->id < shrinker_max_nr.
>>
>> Let's better use memcg_shrinker_nr_max.
> 
> or memcg_nr_shrinker_ids (to match memcg_nr_cache_ids), not sure...
> 
> Come to think of it, this variable is kinda awkward: it is defined in
> vmscan.c but declared in memcontrol.h; it is used by vmscan.c for max
> shrinker id and by memcontrol.c for shrinker map capacity. Just a raw
> idea: what about splitting it in two: one is private to vmscan.c, used
> as max id, say we call it shrinker_id_max; the other is defined in
> memcontrol.c and is used for shrinker map capacity, say we call it
> memcg_shrinker_map_capacity. What do you think?
> 
>>>> +int expand_shrinker_maps(int old_nr, int nr)
>>>> +{
>>>> +	int id, size, old_size, node, ret;
>>>> +	struct mem_cgroup *memcg;
>>>> +
>>>> +	old_size = old_nr / BITS_PER_BYTE;
>>>> +	size = nr / BITS_PER_BYTE;
>>>> +
>>>> +	down_write(&shrinkers_max_nr_rwsem);
>>>> +	for_each_node(node) {
>>>
>>> Iterating over cgroups first, numa nodes second seems like a better idea
>>> to me. I think you should fold for_each_node in memcg_expand_maps.
>>>
>>>> +		idr_for_each_entry(&mem_cgroup_idr, memcg, id) {
>>>
>>> Iterating over mem_cgroup_idr looks strange. Why don't you use
>>> for_each_mem_cgroup?
>>
>> We want to allocate shrinkers maps in mem_cgroup_css_alloc(), since
>> mem_cgroup_css_online() mustn't fail (it's a requirement of currently
>> existing design of memcg_cgroup::id).
>>
>> A new memcg is added to parent's list between two of these calls:
>>
>> css_create()
>>   ss->css_alloc()
>>   list_add_tail_rcu(&css->sibling, &parent_css->children)
>>   ss->css_online()
>>
>> for_each_mem_cgroup() does not see allocated, but not linked children.
> 
> Why don't we move shrinker map allocation to css_online then?
> 
>>  
>>>> +			if (id == 1)
>>>> +				memcg = NULL;
>>>> +			ret = memcg_expand_maps(memcg, node, size, old_size);
>>>> +			if (ret)
>>>> +				goto unlock;
>>>> +		}
>>>> +
>>>> +		/* root_mem_cgroup is not initialized yet */
>>>> +		if (id == 0)
>>>> +			ret = memcg_expand_maps(NULL, node, size, old_size);
>>>> +	}
>>>> +unlock:
>>>> +	up_write(&shrinkers_max_nr_rwsem);
>>>> +	return ret;
>>>> +}

  parent reply	other threads:[~2018-04-24 12:13 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-17 18:52 [PATCH v2 00/12] Improve shrink_slab() scalability (old complexity was O(n^2), new is O(n)) Kirill Tkhai
2018-04-17 18:53 ` [PATCH v2 01/12] mm: Assign id to every memcg-aware shrinker Kirill Tkhai
2018-04-18 14:14   ` Tetsuo Handa
2018-04-18 14:27     ` Kirill Tkhai
2018-04-18 14:32       ` Tetsuo Handa
2018-04-18 15:02         ` Kirill Tkhai
2018-04-22 17:16   ` Vladimir Davydov
2018-04-17 18:53 ` [PATCH v2 02/12] memcg: Refactoring in mem_cgroup_alloc() Kirill Tkhai
2018-04-17 18:53 ` [PATCH v2 03/12] memcg: Refactoring in alloc_mem_cgroup_per_node_info() Kirill Tkhai
2018-04-17 18:53 ` [PATCH v2 04/12] mm: Assign memcg-aware shrinkers bitmap to memcg Kirill Tkhai
2018-04-18 12:55   ` kbuild test robot
2018-04-18 13:05     ` Kirill Tkhai
2018-04-22 17:59   ` Vladimir Davydov
2018-04-23 10:54     ` Kirill Tkhai
2018-04-24 11:28       ` Vladimir Davydov
2018-04-24 11:38         ` Kirill Tkhai
2018-04-24 12:15           ` Vladimir Davydov
2018-04-24 12:24             ` Kirill Tkhai
2018-04-28 15:08               ` Vladimir Davydov
2018-05-03 11:15                 ` Kirill Tkhai
2018-04-24 12:13         ` Kirill Tkhai [this message]
2018-04-23 11:02     ` Kirill Tkhai
2018-04-23 11:06     ` Kirill Tkhai
2018-04-24 11:08       ` Vladimir Davydov
2018-04-17 18:53 ` [PATCH v2 05/12] fs: Propagate shrinker::id to list_lru Kirill Tkhai
2018-04-22 18:03   ` Vladimir Davydov
2018-04-17 18:53 ` [PATCH v2 06/12] list_lru: Add memcg argument to list_lru_from_kmem() Kirill Tkhai
2018-04-17 18:54 ` [PATCH v2 07/12] list_lru: Pass dst_memcg argument to memcg_drain_list_lru_node() Kirill Tkhai
2018-04-17 18:54 ` [PATCH v2 08/12] list_lru: Pass lru " Kirill Tkhai
2018-04-17 18:54 ` [PATCH v2 09/12] mm: Set bit in memcg shrinker bitmap on first list_lru item apearance Kirill Tkhai
2018-04-17 18:54 ` [PATCH v2 10/12] mm: Iterate only over charged shrinkers during memcg shrink_slab() Kirill Tkhai
2018-04-22 18:19   ` Vladimir Davydov
2018-04-17 18:54 ` [PATCH v2 11/12] mm: Add SHRINK_EMPTY shrinker methods return value Kirill Tkhai
2018-04-17 18:54 ` [PATCH v2 12/12] mm: Clear shrinker bit if there are no objects related to memcg Kirill Tkhai
2018-04-22 18:21   ` Vladimir Davydov
2018-04-23 10:01     ` Kirill Tkhai
2018-04-24 10:56       ` Vladimir Davydov

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