From: David Hildenbrand <david@redhat.com>
To: Michal Hocko <mhocko@suse.com>, Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Vlastimil Babka <vbabka@suse.cz>,
Muchun Song <songmuchun@bytedance.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range
Date: Wed, 17 Mar 2021 15:42:43 +0100 [thread overview]
Message-ID: <89830f41-b3f2-a158-a173-8c14101edcaa@redhat.com> (raw)
In-Reply-To: <YFIMtFu/g3jtGqA8@dhcp22.suse.cz>
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
next prev parent reply other threads:[~2021-03-17 14:43 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 11:12 [PATCH v5 0/5] Make alloc_contig_range handle Hugetlb pages Oscar Salvador
2021-03-17 11:12 ` [PATCH v5 1/5] mm,page_alloc: Bail out earlier on -ENOMEM in alloc_contig_migrate_range Oscar Salvador
2021-03-17 14:05 ` Michal Hocko
2021-03-17 14:42 ` David Hildenbrand [this message]
2021-03-17 14:49 ` Michal Hocko
2021-03-18 11:04 ` Oscar Salvador
2021-03-18 11:37 ` Michal Hocko
2021-03-17 11:12 ` [PATCH v5 2/5] mm,compaction: Let isolate_migratepages_{range,block} return error codes Oscar Salvador
2021-03-17 14:12 ` Michal Hocko
2021-03-17 14:38 ` Oscar Salvador
2021-03-17 14:59 ` Michal Hocko
2021-03-18 9:50 ` Vlastimil Babka
2021-03-18 10:22 ` Michal Hocko
2021-03-18 11:10 ` Vlastimil Babka
2021-03-18 11:36 ` Michal Hocko
2021-03-19 9:57 ` Oscar Salvador
2021-03-19 10:14 ` Vlastimil Babka
2021-03-19 10:26 ` Oscar Salvador
2021-03-17 11:12 ` [PATCH v5 3/5] mm: Make alloc_contig_range handle free hugetlb pages Oscar Salvador
2021-03-17 14:22 ` Michal Hocko
2021-03-17 11:12 ` [PATCH v5 4/5] mm: Make alloc_contig_range handle in-use " Oscar Salvador
2021-03-17 14:26 ` Michal Hocko
2021-03-18 8:54 ` Oscar Salvador
2021-03-18 9:29 ` Michal Hocko
2021-03-18 9:59 ` Oscar Salvador
2021-03-18 10:12 ` Michal Hocko
2021-03-17 11:12 ` [PATCH v5 5/5] mm,page_alloc: Drop unnecessary checks from pfn_range_valid_contig Oscar Salvador
2021-03-17 11:15 ` David Hildenbrand
2021-03-17 14:31 ` Michal Hocko
2021-03-17 14:36 ` David Hildenbrand
2021-03-17 15:03 ` Michal Hocko
2021-03-18 8:44 ` Oscar Salvador
2021-03-18 8:55 ` Michal Hocko
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