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 C3E75269CF0; Tue, 17 Jun 2025 13:35:07 +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=1750167309; cv=none; b=sBtqWVNGxvy8r38zIWKgWGBtwk9KEU49WdK1dPtOs3LWApSAVMiFDEyWSqb5OSnu+nDXaQlMFcWZaJ6KEl4uFtzbXuEr4txM/AyOTEU3fNX9SOTii3/6IGG7FIQEwOOETK/YOSS+ejD+wsgl8RKWCvvKF7xm5++No5RDPG6tE/s= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750167309; c=relaxed/simple; bh=4GnMChYZ859nCJCN1piCqEZeHco0KjO/v6zHU+fvsTk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=CzNoArlNz1EhZfgTkiPV9H90S1VJ1Y9rKFZY+DofM/QbUoRw+X28HVz+svA/fQl51FOt8i3kw1zBMuuK71GxXyrHoywTL6HGQQaE5DDxIvyF13UXxjfSrbDrsCkqk+/r+2uAGZSKOIUILMGhlPBFMEDfxGk3WVfHFn6RtX+DeI4= 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=mwWc+jtO; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=7JpNvPqt; 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="mwWc+jtO"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="7JpNvPqt" From: Kurt Kanzenbach DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1750167305; 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=4GnMChYZ859nCJCN1piCqEZeHco0KjO/v6zHU+fvsTk=; b=mwWc+jtO0EL+s3NZP9Z52AznBBTIoMuNIF5GhIJMZE7V2sJx749KMcKZvdfB4wP43lVDq8 84v97VmC2EGwHxXg2Cy6vBADl+pMim9SaHH3j5mMlmGm/iCFjz486pBtLsqT9HR+nBjze5 4DQIjVMyEkymXmo1Nu4AnUGGDGXVLImdVF3LkFFhZnWoZl1W/Iez5ofVrAJfvwN65dx0oI R6ZRfMB1iD6JjYxE0wXKrh8JaRqguoRZaXXMA9aHBnfgNznRoWsvlJZ+bZ037t70hva16K ip3VaPaZG30rLR1BfwOfLAZLJQZRIw+NPmAxokU6+9lslAVVPV7nVmeymoZlfw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1750167305; 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=4GnMChYZ859nCJCN1piCqEZeHco0KjO/v6zHU+fvsTk=; b=7JpNvPqtL1cK8IuFdiKGRKLO2h+WW24bZEhSFTssxtq2UTYXNUnx89ED7pBHeUaqTbsE/+ L/HBD5y6pJ7Ht+CA== To: Marc =?utf-8?Q?Str=C3=A4mke?= , Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Subject: Re: Latency spikes on V6.15.1 Preempt RT and maybe related to intel? IGB In-Reply-To: <19a46896-3d26-415b-9820-730a42b0702e@eltropuls.de> References: <20250613145434.T2x2ML8_@linutronix.de> <20250613195838.0-gZ6bqS@linutronix.de> <97638b0b-cd96-40e2-9dc2-5e6f767b90a4@eltropuls.de> <20250617092814.vqKdu23w@linutronix.de> <20250617100013.1o5lsPLq@linutronix.de> <20250617101507.jU00mupE@linutronix.de> <87v7ou7i4i.fsf@jax.kurt.home> <19a46896-3d26-415b-9820-730a42b0702e@eltropuls.de> Date: Tue, 17 Jun 2025 15:35:03 +0200 Message-ID: <87plf27apk.fsf@jax.kurt.home> Precedence: bulk X-Mailing-List: linux-rt-users@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; charset=utf-8 Content-Transfer-Encoding: quoted-printable On Tue Jun 17 2025, Marc Str=C3=A4mke wrote: > Hi Kurt, > On 17.06.25 12:54, Kurt Kanzenbach wrote: >>> You don't have to live with it. You could add a read after the writes in >>> the loop (wrfl()). This should help. >> Something like this, which was done for Intel e1000? >> >> https://lore.kernel.org/intel-wired-lan/20241219192743.4499-1-gerhard@en= gleder-embedded.com/ >> >> Thanks, >> Kurt > > This works wonders (Latency spike down to 120 us from 700) ! I will=20 > prepare a patch and submit it to LKML. 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