linux-kernel - Re: [PATCH 6/7] memcg: calc NUMA node's weight for scan.

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Date:	Thu, 23 Jun 2011 23:27:10 +0900
From:	Hiroyuki Kamezawa <kamezawa.hiroyuki@...il.com>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	"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>,
	Ying Han <yinghan@...gle.com>,
	"hannes@...xchg.org" <hannes@...xchg.org>
Subject: Re: [PATCH 6/7] memcg: calc NUMA node's weight for scan.

2011/6/23 Michal Hocko <mhocko@...e.cz>:
> On Thu 16-06-11 12:56:33, KAMEZAWA Hiroyuki wrote:
>> From fb8aaa2c5f7fd99dfcb5d2ecb3c1226a58caafea Mon Sep 17 00:00:00 2001
>> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>> Date: Thu, 16 Jun 2011 10:05:46 +0900
>> Subject: [PATCH 6/7] memcg: calc NUMA node's weight for scan.
>>
>> Now, by commit 889976, numa node scan of memcg is in round-robin.
>> As commit log says, "a better algorithm is needed".
>>
>> for implementing some good scheduling, one of required things is
>> defining importance of each node at LRU scanning.
>>
>> This patch defines each node's weight for scan as
>>
>> swappiness = (memcg's swappiness)? memcg's swappiness : 1
>> FILE = inactive_file + (inactive_file_is_low)? active_file : 0
>> ANON = inactive_anon + (inactive_anon_is_low)? active_anon : 0
>>
>> weight = (FILE * (200-swappiness) + ANON * swappiness)/200.
>
> Shouldn't we consider the node size?

Above one cheks FILE+ANON....it's size of node.

> If we have a node which is almost full with file cache and then other
> node wich is much bigger and it is mostly occupied by anonymous memory
> than the other node might end up with higher weight.

I used a porportional fair scheduling in the next patch and I expect I'll not
see heavy starvation of node balancing. And if inactive_anon_is_low(),
the weight of anon-only-node will jump up.

But yes, other "weight" calculation is possible. The point of this patch
series is introducing a scheduler which can handle "weight" of value.

Thanks,
-Kame
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