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@suse.cz님이 작성:
On 7/16/20 9:27 AM, Joonsoo Kim wrote:
2020년 7월 15일 (수) 오후 5:24, Vlastimil Babka vbabka@suse.cz님이 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...
Thanks.