Messages in this thread | | | Subject | Re: [PATCH v5 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range | From | David Hildenbrand <> | Date | Wed, 17 Mar 2021 15:42:43 +0100 |
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On 17.03.21 15:05, Michal Hocko wrote: > On Wed 17-03-21 12:12:47, Oscar Salvador wrote: >> Currently, __alloc_contig_migrate_range can generate -EINTR, -ENOMEM or -EBUSY, >> and report them down the chain. >> The problem is that when migrate_pages() reports -ENOMEM, we keep going till we >> exhaust all the try-attempts (5 at the moment) instead of bailing out. >> >> migrate_pages() bails out right away on -ENOMEM because it is considered a fatal >> error. Do the same here instead of keep going and retrying. > > I suspect this is not really a real life problem, right? The allocation > would be more costly in the end but this is to be expected under a heavy > memory pressure. > > That being said, bailing out early makes sense to me. But now that > you've made me look into the migrate_pages excellent error state reporting > I suspect we have a bug here. Note the > "Returns the number of pages that were not migrated, or an error code." > > but I do not see putback_movable_pages for ret > 0 so it seems we might > leak some pages.
At least in __alloc_contig_migrate_range() we seem to always leave the loop with ret <= 0 and do a putback_movable_pages() with ret < 0.
Which code are you referring to?
(I think the logic flow inside __alloc_contig_migrate_range() might be improved ...)
-- Thanks,
David / dhildenb
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