2020년 7월 17일 (금) 오후 5:15, Vlastimil Babka <vbabka@xxxxxxx>님이 작성: > > On 7/17/20 10:10 AM, Vlastimil Babka wrote: > > 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. > > But then we have e.g. should_reclaim_retry() which calls __zone_watermark_ok() > where ALLOC_CMA plays a role too, so that means we should have alloc_mask set up > correctly wrt ALLOC_CMA at the __alloc_pages_slowpath() level... Good catch! Hmm... Okay. It would be necessarily handled in three places. I will fix it on the next version. Anyway, we need some clean-up about alloc_flags handling since it looks not good for maintenance. Thanks.
