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[109.81.17.175]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4887c8797ecsm18417425e9.8.2026.03.31.00.54.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Mar 2026 00:54:18 -0700 (PDT) Date: Tue, 31 Mar 2026 09:54:16 +0200 From: Michal Hocko To: David Rientjes Cc: Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , 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: 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <371c86c8-1d47-bd70-b74c-769842718b1f@google.com> On Mon 30-03-26 18:20:57, 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 OK, let's go with this and tune it up as we find a need in the future. Acked-by: Michal Hocko Thanks! -- Michal Hocko SUSE Labs