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bh=683KEjyjJdGprwp6x/MvliefPwqxgwCTxqoPXal2rZ4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EUFbtrutIJyOZc8/SOR3PMPupt1r82zh365IH9L0Hra0teTwojAhfwbi1XdGGMZnK PKlBHfNp0vj4A89piR2y3tvMmKgPUIx3bRkkYozH4ImTwZvYgN2NoXkWPexnMPQZem 38Qa3WXmxK+ePiRJiB7wygl8gVx9pblzTS7wqAdAsBpLzWXIgPOVq7l/BgsZBa4qlp NhiUryFRPumaiin43OlJvMh2Aa9dE8MO8q4PCGFjVs/4HZMYHTaZCwy2jbvuzTDUN0 MXW/ptsFujDa5x1AJRA2ea/XABSvchJRug0iEZBAl6ueR2uboM8gCB7ktgjp0E8uUB A2yBwaWMeWJcg== From: SeongJae Park To: David Hildenbrand Cc: SeongJae Park , akpm@linux-foundation.org, osalvador@suse.de, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/memory_hotplug: return zero from do_migrate_range() for only success Date: Wed, 15 Feb 2023 22:33:55 +0000 Message-Id: <20230215223355.102508-1-sj@kernel.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <1ddc2eff-f1bd-be62-3c62-abe6d539feef@redhat.com> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3B970C0004 X-Stat-Signature: wtye9k9iudquo4rzn5ob3jttnct8ikq6 X-HE-Tag: 1676500440-108316 X-HE-Meta: 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 IKUTsp7N d80RuPm0Jie5LDmG/LH3DXubV/LVyo2tF7bqaQbFeN05n2bwIrlBmNwyT7tZfird3xOQ5FENj5qFlEFCZJeEUm2r1/pVWyVhBW/Z1hQnzWXpO2NzqW5AcvvwBlLjuVGEIEw75maxoHTzVFVzxX2RIhUsSwsc8ScIrGbE5m135jdK6AgWKhWfaWj8qsTdwPpzVhXcgPF4g/bRjNed0hluK3i+6XfdlF2/z8WHhpY5IckIrIq5Y08x84aGlqzqt7u//Q8FUcd+5pyY9avo0HD7DAIh68qE6ESdB0PvCgo/pAXuVjjmEI+Y9svT0HVkHQDG4dRg0KIwxK7qY9iSidkL0D4kilConzv0n7megP9jc7CTklMg= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 15 Feb 2023 21:00:50 +0100 David Hildenbrand wrote: > On 15.02.23 19:03, SeongJae Park wrote: > > On Wed, 15 Feb 2023 14:16:05 +0100 David Hildenbrand wrote: > > > >> On 14.02.23 23:32, SeongJae Park wrote: > >>> do_migrate_range() returns migrate_pages() return value, which zero > >>> means perfect success, in usual cases. If all pages are failed to be > >>> isolated, however, it returns isolate_{lru,movalbe}_page() return > >>> values, or zero if all pfn were invalid, were hugetlb or hwpoisoned. So > >>> do_migrate_range() returning zero means either perfect success, or > >>> special cases of isolation total failure. > >>> > >>> Actually, the return value is not checked by any caller, so it might be > >>> better to simply make it a void function. However, there is a TODO for > >>> checking the return value. > >> > >> I'd prefer to not add more dead code ;) Let's not return an error instead. > > > > Makes sense, I will send next spin soon. > > > >> > >> It's still unclear which kind of fatal migration issues we actually care > >> about and how to really detect them. > > > > What do you think about treating the isolation/migration rate limit > > (migrate_rs) hit in do_migrate_range() as fatal? It warns for the event > > already, so definitely a bad sign. > > > > If that's not that bad enough to be treated as fatal, I think we could have yet > > another rate limit to be considered fatal. > > IIRC, there are some setups where offlining might take several minutes > (e.g., heavy O_DIRECT load) and that's to be expected. > > So the existing code warns for better debugging, but keeps trying. So > the ratelimit is rather to not produce too much debug output, not to > really indicate that something is fatal. Thank you for clarification, David! Thanks, SJ > > -- > Thanks, > > David / dhildenb