linux-kernel - Re: [PATCH 7/7] memcg: proportional fair vicitm node selection

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Date:	Fri, 24 Jun 2011 07:20:39 +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 7/7] memcg: proportional fair vicitm node selection

2011/6/23 Michal Hocko <mhocko@...e.cz>:
> On Thu 23-06-11 23:10:11, Hiroyuki Kamezawa wrote:
>> 2011/6/23 Michal Hocko <mhocko@...e.cz>:
>> > On Thu 16-06-11 12:57:41, KAMEZAWA Hiroyuki wrote:
>> >> From 4fbd49697456c227c86f1d5b46f2cd2169bf1c5b Mon Sep 17 00:00:00 2001
>> >> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>> >> Date: Thu, 16 Jun 2011 11:25:23 +0900
>> >> Subject: [PATCH 7/7] memcg: proportional fair node vicitm selection
>> >>
>> >> commit 889976 implements a round-robin scan of numa nodes for
>> >> LRU scanning of memcg at hitting limit.
>> >> But, round-robin is not very good.
>> >>
>> >> This patch implements a proportionally fair victim selection of nodes
>> >> rather than round-robin. The logic is fair against each node's weight.
>> >>
>> >> Each node's weight is calculated periodically and we build an node's
>> >> scheduling entity as
>> >>
>> >>      total_ticket = 0;
>> >>      for_each_node(node)
>> >>       node->ticket_start =  total_ticket;
>> >>         node->ticket_end   =  total_ticket + this_node's_weight()
>> >>         total_ticket = node->ticket_end;
>> >>
>> >> Then, each nodes has some amounts of tickets in proportion to its own weight.
>> >>
>> >> At selecting victim, a random number is selected and the node which contains
>> >> the random number in [ticket_start, ticket_end) is selected as vicitm.
>> >> This is a lottery scheduling algorithm.
>> >>
>> >> For quick search of victim, this patch uses bsearch().
>> >>
>> >> Test result:
>> >>   on 8cpu box with 2 nodes.
>> >>   limit memory to be 300MB and run httpd for 4096files/600MB working set.
>> >>   do (normalized) random access by apache-bench and see scan_stat.
>> >>   The test makes 40960 request. and see scan_stat.
>> >>   (Because a httpd thread just use 10% cpu, the number of threads will
>> >>    not be balanced between nodes. Then, file caches will not be balanced
>> >>    between nodes.)
>> >
>> > Have you also tried to test with balanced nodes? I mean, is there any
>> > measurable overhead?
>> >
>>
>> Not enough yet. I checked OOM trouble this week :).
>>
>> I may need to make another fake_numa setup + cpuset
>> to measurements.
>
> What if you just use NUMA rotor for page cache?
>

Ok, I'll do try in the next week. Thank you for suggestion.

Thanks,
-Kame
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