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Mon, 09 Dec 2024 00:12:32 -0800 (PST) X-Google-Smtp-Source: AGHT+IERxpCGr5FOfh+U40F7TT+UTrCH8cNOIQnKmUp3DkdDwCzxkwMqazGOe3UPcw0ZmgS6DnrG7A== X-Received: by 2002:a05:6000:178a:b0:385:f417:ee46 with SMTP id ffacd0b85a97d-3862b33b786mr8424392f8f.2.1733731952258; Mon, 09 Dec 2024 00:12:32 -0800 (PST) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([185.107.56.30]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3862f02f5c3sm8592429f8f.65.2024.12.09.00.12.31 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 09 Dec 2024 00:12:31 -0800 (PST) Message-ID: <94c05164fe0bc0b0f52fec3a1d21e0b836fbdf54.camel@redhat.com> Subject: Re: [PATCH] sched: Move task_mm_cid_work to mm delayed work From: Gabriele Monaco To: linux-kernel@vger.kernel.org Date: Mon, 09 Dec 2024 09:12:30 +0100 In-Reply-To: <445b4203-940d-4817-bd45-9da757f22450@efficios.com> References: <20241205083110.180134-2-gmonaco@redhat.com> <4c067b75e06aadd34eff5b60fc7c59967aa30809.camel@redhat.com> <5ba975e2-06b9-4b98-bece-d601b19a06db@efficios.com> <445b4203-940d-4817-bd45-9da757f22450@efficios.com> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0ByZWRoYXQuY29tPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmbiuWMCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfJzZgD/TXjnqCyqaZH/Y2w+YVbvm93WX2eqBqiVZ6VEjTuGNs8A/iPrKbzdWC7AicnK xyhmqeUWOzFx5P43S1E1dhsrLWgP Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.54.2 (3.54.2-1.fc41) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2024-12-06 at 09:06 -0500, Mathieu Desnoyers wrote: > > Thinking back on this, you'll want a program that does the following > on a system with N CPUs: > > - Phase 1: run one thread per cpu, pinned on each cpu. Print the > mm_cid from each thread with the cpu number every second or so. > > - Exit all threads except the main thread, join them from the main > thread, > > - Phase 2: the program is now single-threaded. We'd expect the > mm_cid value to converge towards 0 as the periodic task clears > unused CIDs. > > So I think in phase 2 we can have an actual automated test: If after > an order of magnitude more time than the 100ms delay between periodic > tasks we still observe mm_cid > 0 in phase 2, then something is > wrong. > > Thoughts ? Nice idea, that looks neat and fairly simple. Also by printing every second we would get the threads running in short bursts and, probably, the test would fail with the current implementation, depending how long we wait, of course. I can try to draft something to test my implementation. Thanks, Gabriele