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[82.17.115.212]) by smtp.gmail.com with ESMTPSA id y14sm2729448wmj.37.2021.05.18.07.05.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 May 2021 07:05:55 -0700 (PDT) Date: Tue, 18 May 2021 15:05:54 +0100 From: Aaron Tomlin To: Michal Hocko Cc: linux-mm@kvack.org, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Vlastimil Babka Subject: Re: [PATCH] mm/page_alloc: try oom if reclaim is unable to make forward progress Message-ID: <20210518140554.dwan66i4ttmzw4hj@ava.usersys.com> X-PGP-Key: http://pgp.mit.edu/pks/lookup?search=atomlin%40redhat.com X-PGP-Fingerprint: 7906 84EB FA8A 9638 8D1E 6E9B E2DE 9658 19CC 77D6 References: <20210315165837.789593-1-atomlin@redhat.com> <20210319172901.cror2u53b7caws3a@ava.usersys.com> <20210325210159.r565fvfitoqeuykp@ava.usersys.com> <20210326112254.jy5jkiwtgj3pqkt2@ava.usersys.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="4oj4tq5xtvq4w6dd" Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --4oj4tq5xtvq4w6dd Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Michal, On Fri 2021-03-26 16:36 +0100, Michal Hocko wrote: > OK, I kinda expected this would be not easily reproducible. Unfortunately, I'm still waiting for feedback on this. > We should be focusing on the compaction retry logic and see whether we > can have some "run away" scenarios there. Seeing so many retries without > compaction bailing out sounds like a bug in that retry logic. I suspect so. This is indeed a case of excessive reclaim/compaction retries (i.e. the last known value stored in the no_progress_loops variable was 31,611,688). What might be particularly unique about this situation is that a fatal signal was found pending. In this context, if I understand correctly, it does not make sense to retry compaction when the last known compact result was skipped and a fatal signal is pending. Looking at try_to_compact_pages(), indeed COMPACT_SKIPPED can be returned; albeit, not every zone, on the zone list, would be considered in the case a fatal signal is found to be pending. Yet, in should_compact_retry(), given the last known compaction result, each zone, on the zone list, can be considered/or checked (see compaction_zonelist_suitable()). If a zone e.g. was found to succeed then reclaim/compaction would be tried again (notwithstanding the above). --=20 Aaron Tomlin --4oj4tq5xtvq4w6dd Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEeQaE6/qKljiNHm6b4t6WWBnMd9YFAmCjybAACgkQ4t6WWBnM d9a+MBAAmH76h+vl0MTKp+BW4YxqXL9f0lULDieShMJQys2khOOQSuRcnFIsuCM3 fg2AuDFB8SgKY++gws6+ardG9i6jtNRFEczsK0ZFwwvUzxo5TOZ78EE8/PaMeAcv z5o2pAGdSBARUGgBzNVzur60uGekXjiq2nG3shuU1BtgUiki1M3xXfzHFofvbrM7 LPzIdnXUxmGVsMORH0raYkSdZNbP5xY2lKHCoUu/NpkVsqcRENNRwULgFIiDKexJ tRG1eOjDuJ0R7j5jTOIlsDtIuSdg2YAUEE1YNqt+05LvF7RjuRcKedlaelirw3Wv cuNTxFw0YBj8xLxcIBPzayzF0w480OAZg9jkC8RbRI/1scd5tp3GiEVPawiwFcHH GLg9FP2Y7qRDCymy2kurpW5xHnAj5gX0WvrApBXmTUR1eowwy27iRu39lvqN4k8P LAXSpk+YmQm231YuSv4qn9wGoIrzBwTWISMZL8vUW0oJ+TikSqEzenptOBm2HSQd U++Jyv8+ChbiiZan+spabF8RsOzKip0afwMNqzaOfklJ8DMy7PiCw6AAwI304LGj Bua6ba3UzY2/NXjJRqnNNWBUg2i50nm9YsuS4h5sLbWwaKimG6TAHnayeoBUdCgP 45lMlrofia3baPxitQfsPbc51N37T/y1uQLZU4ui42EhCKB8bw0= =onqo -----END PGP SIGNATURE----- --4oj4tq5xtvq4w6dd--