From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) (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 AC3B83F0A95; Fri, 26 Jun 2026 10:27:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.17 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782469638; cv=none; b=j4hpYOYWVpvHvi36GQvl0SJNu2THTYXiIMbTGWRuZgkjgtufwZYyz1Ef7yRhexvEc37Pl1Bt4F9mkY5/ZkGkeTpPVjJ6qf6ZzATStUpvhdxl8QAMRkEBZeqwVHlX+WVw7zR867qkK2mwCGyVHfvsb8vGF1lWRf/t/EeP8BqUucw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782469638; c=relaxed/simple; bh=gIk0JBnO1KbqU0wbDh9FxwJA+SGKakNdkm1qDWkeojY=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=BxYx185G1X+xXyKpaUqn9ren3saEIVMA6bGAC4Ap4VbKxC30c81I+5ue11RAFgab8/xAQcdwk1Zb59sz8UqPj9/r1ujFJTAzwFzJU5WjiuTWihULZ9t+UdpL1W0wRMlhR4Zcxp3mnYkptdUzw266/8i/F2aDXPsVy5KLJY1RdAQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org; spf=pass smtp.mailfrom=goodmis.org; arc=none smtp.client-ip=216.40.44.17 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=goodmis.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=goodmis.org Received: from omf08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 319321C5F21; Fri, 26 Jun 2026 10:27:04 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf08.hostedemail.com (Postfix) with ESMTPA id 5417F20025; Fri, 26 Jun 2026 10:27:01 +0000 (UTC) Date: Fri, 26 Jun 2026 06:26:58 -0400 From: Steven Rostedt To: Valentin Schneider Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Masami Hiramatsu , Mathieu Desnoyers , Tomas Glozar , Costa Shulyupin , Crystal Wood , John Kacur , Ivan Pravdin , Jonathan Corbet Subject: Re: [RFC PATCH v2 0/4] tracing/osnoise: Track IPIs Message-ID: <20260626062658.7f95bcad@fedora> In-Reply-To: <20260617131803.2988989-1-vschneid@redhat.com> References: <20260617131803.2988989-1-vschneid@redhat.com> X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 5417F20025 X-Stat-Signature: kkf8dp3i6gqctkje4wxpghb5n9mmb6cf X-Rspamd-Server: rspamout06 X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX19G6m87l64apJQvK49UW7rP/8WnSn6Erpo= X-HE-Tag: 1782469621-445287 X-HE-Meta: U2FsdGVkX19EXOYuDnf6v/9daXPzxItIb3MQSLn14e1imUt8I74EJzh4OdzyEFaS8PL9CvbUvBfPMT/c59T326mQl5p/JBb8j6ROrZCoElLMi2nxiXt+JkHufRQpoAZMCk+/IGYBrnB9459yEp3IaT5JLL+l8HGrUJZDsTYcbPjPayPdoIBxwFdpX/anSGo5WxW+AhwxPe19uqjrYhqxnpZq6ChMw7PQogk29B+BXleU2Xyhp+bhWnWMen5YWSVpQ9JErNgQyF0US00rTZO6p72gkEy3tsWtbAm6d3iUgbQGc9snkCy6XIOxGWxR0Lc220ZCHvH6bovBkcPynxlttWnHw2Ge1zSB On Wed, 17 Jun 2026 15:17:55 +0200 Valentin Schneider wrote: > Hi folks, >=20 > So I've seen a few times now reports of latency spikes caused by IPIs, us= ually > because of isolation misconfiguration, but only detected at the tail of e= nd > e.g. a 24h timerlat run. >=20 > It's not because those IPIs are rare, but rather that they don't by thems= elves > cause a monitered CPU to reach the latency threshold, it's usually a comb= ined > interference that gets us there. >=20 > I'd like to make it easier to detect such misconfigurations and thus IPIs > hitting supposedly-isolated CPUs. I initially kludged a timerlat option t= o stop > tracing as soon as an IPI was sent to a monitored CPU, regardless of the = latency > threshold. It sort of did the trick, but Tom=C3=A1=C5=A1 convinced me tim= erlat wasn't > really the place for that. >=20 > So here's IPI tracking added to osnoise. This time around fully in usersp= ace, as > Tom=C3=A1=C5=A1 pointed out to me that this will make it a lot easier to = deploy to older > kernels. >=20 > Based on top of linux/next at 'next-20260616' to have the latest libsubcmd > changes. > =20 Hi Valentin, My new job actually makes me very interested in IPI interference, and this patch set looks *very* interesting. I'm currently finishing up my orientation and hopefully next week I can start catching up on all my email. I'll try to take a deeper look at this in the coming weeks. -- Steve