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From: Shakeel Butt To: David Rientjes Cc: Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Petr Mladek , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [patch v3] mm, page_alloc: reintroduce page allocation stall warning Message-ID: <20260331030102.GA615109@shakeel.butt@linux.dev> References: <30945cc3-9c4d-94bb-e7e7-dde71483800c@google.com> <231154f8-a3c3-229a-31a7-f91ab8ec1773@google.com> <58a10940-e44c-a120-dd6e-ee9f480c4946@google.com> <371c86c8-1d47-bd70-b74c-769842718b1f@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <371c86c8-1d47-bd70-b74c-769842718b1f@google.com> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Queue-Id: 40E654000D X-Stat-Signature: 3zro6t58z6mfyhbxsw9ueqskxo4px48c X-Rspamd-Server: rspam06 X-HE-Tag: 1774926159-952985 X-HE-Meta: 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 fbM7eHZ7 ZpFUHUTs3xHKPUfpzCx3haXo15NoxYcaU4s8H27GjmjMEaidS5dG//3to5607LdUxWaRxKQe2NRM8eCM3HTHkMwqtdQ69tnQ79ZNPHWZem9an5roRTDKJD/B4ZyOgvkC35pSkwFFx+kB2nnjqIYuJNAwUI+4jMzmfxI0SkB/tnniuvOSpe/1LIu1cFwSvf6gBYjJeRHLN75bQwq4EOOR8BRV3Eg2BOVJEmTjlM2zHZ4wROCUl/8i+M8nCRVMWMUwYa/ClLkXbC+sUX4lUuUPwpyOaLXqnII5pc8RnCvDnGKGZQtk= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 30, 2026 at 06:20:57PM -0700, David Rientjes wrote: > Previously, we had warnings when a single page allocation took longer > than reasonably expected. This was introduced in commit 63f53dea0c98 > ("mm: warn about allocations which stall for too long"). > > The warning was subsequently reverted in commit 400e22499dd9 ("mm: don't > warn about allocations which stall for too long") because it was possible > to generate memory pressure that would effectively stall further progress > through printk execution. > > Page allocation stalls in excess of 10 seconds are always useful to debug > because they can result in severe userspace unresponsiveness. Adding > this artifact can be used to correlate with userspace going out to lunch > and to understand the state of memory at the time. > > There should be a reasonable expectation that this warning will never > trigger given it is very passive, it will only be emitted when a page > allocation takes longer than 10 seconds. If it does trigger, this > reveals an issue that should be fixed: a single page allocation should > never loop for more than 10 seconds without oom killing to make memory > available. > > Unlike the original implementation, this implementation only reports > stalls once for the system every 10 seconds. Otherwise, many concurrent > reclaimers could spam the kernel log unnecessarily. Stalls are only > reported when calling into direct reclaim. > > Acked-by: Vlastimil Babka (SUSE) > Signed-off-by: David Rientjes Reviewed-by: Shakeel Butt I am hoping that the reason you are reintroducing these warnings is because you already are seeing such cases in your production environment. Do you have anything interesting to share?