From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) (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 AC19531A813 for ; Thu, 26 Feb 2026 00:48:15 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=216.40.44.15 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772066897; cv=none; b=BNUva8W4BCL4hYUZnaIiLGSFxMVg2WmcJVUqBIQ0Ez90DqLv6ywwxb/8ZsyopiWlej1ntjgt2IG/gZNUj4CUA908UbnXJwY3GqFkWCRWn3videz0GD2Ut6zsYMV2zo/uysPaivHc8rMM7B2SXUqMOjuYcSCikzP4ftMYp5mTwoo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772066897; c=relaxed/simple; bh=+nScr5O+8XN72KsthIHdBfbcTb5RkEHQc09X7joplhM=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=OrPhhs9zxUJrvelsoOtJAGIy8NTz43AHdwbzlMyZ9ITEGgr2fppXw8pYT/VP8cGyq7Fb54l7KYhO43RSb7AgF9i2m9xsPxzqiuBx4/9veF9gZdpk6jvpP4F/+GhvvvtbtdGRkYoEw8cl6iZdSoywnUer5Kc8Wq4zr1B0rKnRrIk= 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=216.40.44.15 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 omf09.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 540521402AD; Thu, 26 Feb 2026 00:48:13 +0000 (UTC) Received: from [HIDDEN] (Authenticated sender: rostedt@goodmis.org) by omf09.hostedemail.com (Postfix) with ESMTPA id 6F0512002A; Thu, 26 Feb 2026 00:48:10 +0000 (UTC) Date: Wed, 25 Feb 2026 19:48:09 -0500 From: Steven Rostedt To: Peter Zijlstra Cc: Shrikanth Hegde , juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, clrkwllms@kernel.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Linus Torvalds , mingo@kernel.org, Thomas Gleixner , Sebastian Andrzej Siewior Subject: Re: [PATCH] sched: Further restrict the preemption modes Message-ID: <20260225194809.1f5e44a6@fedora> In-Reply-To: <20260225105345.GZ1282955@noisy.programming.kicks-ass.net> References: <20251219101502.GB1132199@noisy.programming.kicks-ass.net> <20260225105345.GZ1282955@noisy.programming.kicks-ass.net> X-Mailer: Claws Mail 4.3.1 (GTK 3.24.51; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: eh913opgghia1ai67mntnx7y3qsoyeyf X-Rspamd-Server: rspamout03 X-Rspamd-Queue-Id: 6F0512002A X-Session-Marker: 726F737465647440676F6F646D69732E6F7267 X-Session-ID: U2FsdGVkX1+LmxV/qj/B89LDSV/0R5PkTrk0iwFxs90= X-HE-Tag: 1772066890-966173 X-HE-Meta: U2FsdGVkX18Hf6RrxK3ZQAFIveO7+KKflbA0hChrE5zmj4PsZ2DcqeDR0MAojM1rEvL9V0Tzc8NtyrElDEp38SuV9ebmvj441F49DdkSDwEL1arFn7MXoUGIy1lwFUbhVXWjkFxlDuWMONRFHsc7BxS7EnHD/hLA94nE1qG0QunMOKRtaPrrV7c7eYVzISvSVeTy+lEqM9U/lt74ojUDdKoRvu+LjTgs9LOsj0Ua+Ttg1zzbsgGzBfBjZpWGRBukHOAxSq/NpmlcbBYefZiNVJxBA/wjGGHJuvf6cresgSDVKZHEAusDDHUZiiK/F3jzSYDSSEve27YCaB5Qa7dRZLoPyHBjUWa+8JwYwbJqEat0Ysx+Ylw7kKmtSMN4De13 On Wed, 25 Feb 2026 11:53:45 +0100 Peter Zijlstra wrote: > Oh, that reminds me, Steve, would it make sense to have > task_struct::se.sum_exec_runtime as a trace-clock? That's unique per task right? As tracing is global it requires the clock to be monotonic, and I'm guessing a single sched_switch will break that. Now if one wants to trace how long kernel paths are, I'm sure we could trivially make a new tracer to do so. echo max_kernel_time > current_tracer or something like that, that could act like a latency tracer that monitors how long any kernel thread runs without being preempted. -- Steve