linux-kernel - Re: Suspicious error for CMA stress test

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Message-ID: <56E94B89.80706@suse.cz>
Date:	Wed, 16 Mar 2016 13:03:21 +0100
From:	Vlastimil Babka <vbabka@...e.cz>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	Joonsoo Kim <iamjoonsoo.kim@....com>,
	"Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>,
	Laura Abbott <labbott@...hat.com>,
	Hanjun Guo <guohanjun@...wei.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sasha Levin <sasha.levin@...cle.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	qiuxishi <qiuxishi@...wei.com>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <will.deacon@....com>,
	Arnd Bergmann <arnd@...db.de>,
	dingtinahong <dingtianhong@...wei.com>, chenjie6@...wei.com,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: Suspicious error for CMA stress test

On 03/14/2016 03:10 PM, Joonsoo Kim wrote:
> 2016-03-14 21:30 GMT+09:00 Vlastimil Babka <vbabka@...e.cz>:
>
> Now I see why this happen. I enabled CONFIG_DEBUG_PAGEALLOC
> and it makes difference.
>
> I tested on x86_64, gcc (Ubuntu 4.8.4-2ubuntu1~14.04.1) 4.8.4.
>
> With CONFIG_CMA + CONFIG_DEBUG_PAGEALLOC
> ./scripts/bloat-o-meter page_alloc_base.o page_alloc_vlastimil_orig.o
> add/remove: 0/0 grow/shrink: 2/0 up/down: 510/0 (510)
> function                                     old     new   delta
> free_one_page                               1050    1334    +284
> free_pcppages_bulk                          1396    1622    +226
>
> ./scripts/bloat-o-meter page_alloc_base.o page_alloc_mine.o
> add/remove: 0/0 grow/shrink: 2/0 up/down: 351/0 (351)
> function                                     old     new   delta
> free_one_page                               1050    1230    +180
> free_pcppages_bulk                          1396    1567    +171
>
>
> With CONFIG_CMA + !CONFIG_DEBUG_PAGEALLOC
> (pa_b is base, pa_v is yours and pa_m is mine)
>
> ./scripts/bloat-o-meter pa_b.o pa_v.o
> add/remove: 0/0 grow/shrink: 1/1 up/down: 88/-23 (65)
> function                                     old     new   delta
> free_one_page                                761     849     +88
> free_pcppages_bulk                          1117    1094     -23
>
> ./scripts/bloat-o-meter pa_b.o pa_m.o
> add/remove: 0/0 grow/shrink: 2/0 up/down: 329/0 (329)
> function                                     old     new   delta
> free_one_page                                761    1031    +270
> free_pcppages_bulk                          1117    1176     +59
>
> Still, it has difference but less than before.
> Maybe, we are still using different configuration. Could you
> check if CONFIG_DEBUG_VM is enabled or not? In my case, it's not

It's disabled here.

> enabled. And, do you think this bloat isn't acceptable?

Well, it is quite significant. But given that Hanjun sees the errors 
still, it's not the biggest issue now :/

> Thanks.
>