From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 675232609EE; Thu, 5 Mar 2026 08:55:56 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772700957; cv=none; b=rQfYkgq0Py5WSo3eIQ+ZkIajujNr2kRBr4BhSmPD5U2xqBYbuIDxULkcX65EpaZSVIsa41ruXfysiVsxhQQsBsqteJsQYvrADo9Zbve7cLK0PpiLIxkYK8aTKcwdbNY62b4T1gJUWYkPa1x2wM77iB2jtkvNHHpHh84bajIF5MI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772700957; c=relaxed/simple; bh=tdiSSpWSH2rXlDO+aTYlglUyAiN13r4ToBuz0sTUbGw=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=g4axjh4pEkjHKU1nUbBoYPtpaBvN1q0AGQCixt3w/DZE8LaNs/aBw6oQZ+jVjhODhzgUYq8/n7uWYSHtAR0gqpkN/+uQSNxFoVhr7F8AHguHJUiP97yUlPiDyXBX7/3Mi4nKSIepCCZZFwX5HjBAvefA7Bf/JvUSD85Gpsg9ttw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=g8zxm0UO; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=57KdUgHm; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="g8zxm0UO"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="57KdUgHm" From: Kurt Kanzenbach DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1772700954; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ecqro3YS78h33SUaUsJYIVaoB0LHuu2VIDT6L98U+ZU=; b=g8zxm0UO+kYJydvh1gWJZkCT+dKwS0pl90SUdHLmfQ4K5Lm0U3H+xs52y/+nZILqf+Vt2h 00zGgW4a/bQM3PPFHLF8Q26jDBJvgnptZrTX8zlvbncO13NhMIzCkZIj1bb3MLA5YakQIr 3yNg9jbqq2Av2G169EYRFyBy4PWiOkb5ZeXHvHDAqjCUamFegvw5gA6aTGPLf6Lalc4R2r Lluv6c/YXLRXkJap4FaxyL9Utv05JihGu6oAjCPc7fqFu9iDedvKeDn+HoFZL9af26+6mx GqLtl+RovxzqBh5l2T+PZQY6KHxgCMPcN07IP2Utl3j3VXkcAeu6TpRlsrensA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1772700954; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ecqro3YS78h33SUaUsJYIVaoB0LHuu2VIDT6L98U+ZU=; b=57KdUgHm8XZ5ZyAILCqJCRhioJDmsfvZQ4foBQSX4OSPxosP3hojz58idK/qgceU9NqX4y Gj1t5GqqfGthbbCQ== To: Miroslav Lichvar Cc: Paul Menzel , Tony Nguyen , Przemek Kitszel , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Richard Cochran , Vinicius Costa Gomes , Sebastian Andrzej Siewior , Vadim Fedorenko , Jacob Keller , intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH iwl-next v4] igb: Retrieve Tx timestamp from BH workqueue In-Reply-To: References: <20260303-igb_irq_ts-v4-1-cbae7f127061@linutronix.de> <9805389e-9ea4-4e7a-a122-65f733ead33c@molgen.mpg.de> <87qzq1rq2k.fsf@jax.kurt.home> Date: Thu, 05 Mar 2026 09:55:52 +0100 Message-ID: <87seae4puv.fsf@jax.kurt.home> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" --=-=-= Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed Mar 04 2026, Miroslav Lichvar wrote: > On Tue, Mar 03, 2026 at 02:38:11PM +0100, Kurt Kanzenbach wrote: >> > It would be great, if you shared the numbers. Did Miroslav already tes= t=20 >> > this? >>=20 >> Great question. I did test with ptp4l and synchronization looks fine < >> below 10ns back to back as expected. I did not test with ntpperf, >> because I was never able to reproduce the NTP regression to the same >> extent as Miroslav reported. Therefore, Miroslav is on Cc in case he >> wants to test it. Let's see. > > I ran the same test with I350 as before and there still seems to be a > regression, but interestingly it's quite different to the previous versio= ns of > the patch. It's like there is a load-sensitive on/off switch. > > Without the patch: > > | responses | response time (ns) > rate clients | lost invalid basic xleave | min mean max s= tddev > 150000 15000 0.00% 0.00% 0.00% 100.00% +4188 +36475 +193328 = 16179 > 157500 15750 0.02% 0.00% 0.02% 99.96% +6373 +42969 +683894 = 22682 > 165375 16384 0.03% 0.00% 0.00% 99.97% +7911 +43960 +692471 = 24454 > 173643 16384 0.06% 0.00% 0.00% 99.94% +8323 +45627 +707240 = 28452 > 182325 16384 0.06% 0.00% 0.00% 99.94% +8404 +47292 +722524 = 26936 > 191441 16384 0.00% 0.00% 0.00% 100.00% +8930 +51738 +223727 = 14272 > 201013 16384 0.05% 0.00% 0.00% 99.95% +9634 +53696 +776445 = 23783 > 211063 16384 0.00% 0.00% 0.00% 100.00% +14393 +54558 +329546 = 20473 > 221616 16384 2.59% 0.00% 0.05% 97.36% +23924 +321205 +518192 = 21838 > 232696 16384 7.00% 0.00% 0.10% 92.90% +33396 +337709 +575661 = 21017 > 244330 16384 10.82% 0.00% 0.15% 89.03% +34188 +340248 +556237 = 20880 > > With the patch: > 150000 15000 5.11% 0.00% 0.00% 94.88% +4426 +460642 +640884 = 83746 > 157500 15750 11.54% 0.00% 0.26% 88.20% +14434 +543656 +738355 = 30349 > 165375 16384 15.61% 0.00% 0.31% 84.08% +35822 +515304 +833859 = 25596 > 173643 16384 19.58% 0.00% 0.37% 80.05% +20762 +568962 +900100 = 28118 > 182325 16384 23.46% 0.00% 0.42% 76.13% +41829 +547974 +804170 = 27890 > 191441 16384 27.23% 0.00% 0.46% 72.31% +15182 +557920 +798212 = 28868 > 201013 16384 30.51% 0.00% 0.49% 69.00% +15980 +560764 +805576 = 29979 > 211063 16384 0.06% 0.00% 0.00% 99.94% +12668 +80487 +410555 = 62182 > 221616 16384 2.94% 0.00% 0.05% 97.00% +21587 +342769 +517566 = 23359 > 232696 16384 6.94% 0.00% 0.10% 92.96% +16581 +336068 +484574 = 18453 > 244330 16384 11.45% 0.00% 0.14% 88.41% +23608 +345023 +564130 = 19177 > > At 211063 requests per second and higher the performance looks the > same. But at the lower rates there is a clear drop. The higher > mean response time (difference between server TX and RX timestamps) > indicates more of the provided TX timestamps are hardware timestamps > and the chrony server timestamp statistics confirm that. > > So, my interpretation is that like with the earlier version of the > patch it's trading performance for timestamp quality at lower rates, > but unlike the earlier version it's not losing performance at the > higher rates. That seems acceptable to me. Admins of busy servers > might need to decide if they should keep HW timestamping enabled. In > theory, chrony could have an option to do that automatically. Great! Thanks a lot for testing and sharing your numbers. I'll send v5 then with updated changelog as suggested by Aleksandr and Paul. 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