Re: Suspicious error for CMA stress test

From: Vlastimil Babka
Date: Wed Mar 16 2016 - 08:03:37 EST


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

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.