Re: Suspicious error for CMA stress test

Vlastimil Babka
2016-03-16T12:03:33Z

On 03/14/2016 03:10 PM, Joonsoo Kim wrote:
> 2016-03-14 21:30 GMT+09:00 Vlastimil Babka <vbabka@suse.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.
>