On 7/17/20 9:29 AM, Joonsoo Kim wrote:
> 2020년 7월 16일 (목) 오후 4:45, Vlastimil Babka <vbabka@xxxxxxx>님이 작성:
>>
>> On 7/16/20 9:27 AM, Joonsoo Kim wrote:
>> > 2020년 7월 15일 (수) 오후 5:24, Vlastimil Babka <vbabka@xxxxxxx>님이 작성:
>> >> > /*
>> >> > * get_page_from_freelist goes through the zonelist trying to allocate
>> >> > * a page.
>> >> > @@ -3706,6 +3714,8 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
>> >> > struct pglist_data *last_pgdat_dirty_limit = NULL;
>> >> > bool no_fallback;
>> >> >
>> >> > + current_alloc_flags(gfp_mask, &alloc_flags);
>> >>
>> >> I don't see why to move the test here? It will still be executed in the
>> >> fastpath, if that's what you wanted to avoid.
>> >
>> > I want to execute it on the fastpath, too. Reason that I moved it here
>> > is that alloc_flags could be reset on slowpath. See the code where
>> > __gfp_pfmemalloc_flags() is on. This is the only place that I can apply
>> > this option to all the allocation paths at once.
>>
>> But get_page_from_freelist() might be called multiple times in the slowpath, and
>> also anyone looking for gfp and alloc flags setup will likely not examine this
>> function. I don't see a problem in having it in two places that already deal
>> with alloc_flags setup, as it is now.
>
> I agree that anyone looking alloc flags will miss that function easily. Okay.
> I will place it on its original place, although we now need to add one
> more place.
> *Three places* are gfp_to_alloc_flags(), prepare_alloc_pages() and
> __gfp_pfmemalloc_flags().
Hm the check below should also work for ALLOC_OOM|ALLOC_NOCMA then.
/* Avoid allocations with no watermarks from looping endlessly */
if (tsk_is_oom_victim(current) &&
(alloc_flags == ALLOC_OOM ||
(gfp_mask & __GFP_NOMEMALLOC)))
goto nopage;
Maybe it's simpler to change get_page_from_freelist() then. But document well.
> Thanks.
>
