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Tue, 01 Sep 2026 00:37:31 -0700 (PDT) Received: from gmonaco-thinkpadt14gen3.rmtit.csb ([195.174.135.130]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49b91c5790csm286144315e9.0.2026.09.01.00.37.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Sep 2026 00:37:30 -0700 (PDT) Message-ID: <0b0b115713a6d5a10d719085284dc7cef21ed892.camel@redhat.com> Subject: Re: [RFC 1/3] rv: add per-edge dwell-time statistics primitive From: Gabriele Monaco To: Tobias Schaffner , Steven Rostedt Cc: Jonathan Corbet , Shuah Khan , Masami Hiramatsu , Mathieu Desnoyers , Jan Kiszka , Philippe Gerum , linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 01 Sep 2026 09:37:28 +0200 In-Reply-To: <20260827072400.45734-2-tobias.schaffner@siemens.com> References: <20260827072400.45734-1-tobias.schaffner@siemens.com> <20260827072400.45734-2-tobias.schaffner@siemens.com> Autocrypt: addr=gmonaco@redhat.com; prefer-encrypt=mutual; keydata=mDMEZuK5YxYJKwYBBAHaRw8BAQdAmJ3dM9Sz6/Hodu33Qrf8QH2bNeNbOikqYtxWFLVm0 1a0JEdhYnJpZWxlIE1vbmFjbyA8Z21vbmFjb0BrZXJuZWwub3JnPoiZBBMWCgBBFiEEysoR+AuB3R Zwp6j270psSVh4TfIFAmjKX2MCGwMFCQWjmoAFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4AACgk Q70psSVh4TfIQuAD+JulczTN6l7oJjyroySU55Fbjdvo52xiYYlMjPG7dCTsBAMFI7dSL5zg98I+8 cXY1J7kyNsY6/dcipqBM4RMaxXsOtCRHYWJyaWVsZSBNb25hY28gPGdtb25hY29AcmVkaGF0LmNvb T6InAQTFgoARAIbAwUJBaOagAULCQgHAgIiAgYVCgkICwIEFgIDAQIeBwIXgBYhBMrKEfgLgd0WcK eo9u9KbElYeE3yBQJoymCyAhkBAAoJEO9KbElYeE3yjX4BAJ/ETNnlHn8OjZPT77xGmal9kbT1bC1 7DfrYVISWV2Y1AP9HdAMhWNAvtCtN2S1beYjNybuK6IzWYcFfeOV+OBWRDQ== User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: FIk0hTJI25p0OLYBz4HpqEZKygt4xxnXYEBOjDasJXs_1788248251 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Thu, 2026-08-27 at 09:23 +0200, Tobias Schaffner wrote: > +=09while (dwell_ns > (u64)max) { > +=09=09s64 prev =3D local64_cmpxchg(&s->max_ns, max, dwell_ns); > + > +=09=09if (prev =3D=3D max) > +=09=09=09break; > +=09=09max =3D prev; > +=09} try_cmpxchg() functions produce arguably cleaner code, would you mind doing= : while (dwell_ns > (u64)max) { if (local64_try_cmpxchg(&s->max_ns, &max, dwell_ns)) break; } Also, although issues are practically impossible, I'd avoid an unbound loop= in hot paths, you could go up to MAX_DA_RETRY_RACING_EVENTS (already existing = in da_monitor) and put some warning in case you reach the maximum amount of retries. Thanks, Gabriele