From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) (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 8B0791EA7C6; Thu, 6 Feb 2025 13:58:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=90.155.50.34 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738850288; cv=none; b=UcrpLtl7ap33Ywe8PFx2rQGvR5JTIsQioXagN5VNRrYFKIjp04eUd0z82Bsq7yM5C/y9hs6pLazBiuUIXUJ16ntUyMo6SjgKe8cAfVQBBvd/UaIEWVEKvQyAEObo6TgqD+1Kc1fxfjzMWSt9BS/fHieZadKaTSL+259KBxdFBMM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1738850288; c=relaxed/simple; bh=cEhkfPaoicf2zxAScAcOmhV+Jht47Dii7DLMmmIYkC4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=EvO3bHP7pJqhIqRNPp43ZF94spNQ9zo3PbCBZqVDisE8GdtfBH2p5AQWletB7n9VdG8B5KXN3ivxpKy8/G6tDKE6KXCXSxjlMcoRBk3Uz3CGAsAQlUuCmTuTbX4y7FLfiF9oKPa2zreLlWk27I9ULr4qv9XAFA48tQJiG87EHBA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org; spf=none smtp.mailfrom=infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=qFAwRwU9; arc=none smtp.client-ip=90.155.50.34 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="qFAwRwU9" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=aS8G2mLVXo/L1oMuqtZDMH9m5wICqaE0EgdSFqltFMQ=; b=qFAwRwU94EzqKbEILUMXjByVGu JJUSIYThEUJtvIxP64w/gKtfzM6b27fey57XMLUMpS/KXaNn0cCKxSiHGGPQzWuNbLAbzhWA+r/Ku MychWV9G2HX0R3YVIouwsRdbEu/CR82pZr5Xd8D5PNzyBJPoabJPnmNyQAZ2c9zw3e6Pn3IMsM7Nq 8B7w7WH0BdIVUjvQG89CwZo7NMODIyVO5WSPm7SboBMh5rFiJvdFbsSzbN0iNKnv1NecjbtIIaV7U GtNwR/t/gAZeKGy9ZD97CTVPQ25AGA20AVxOtwZ7YGrRT5+0/8VyPgZjSOrhzbi/j0BKytkEQnH4G LzO0Kbow==; Received: from 77-249-17-252.cable.dynamic.v4.ziggo.nl ([77.249.17.252] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.98 #2 (Red Hat Linux)) id 1tg2O1-000000065sw-1yNY; Thu, 06 Feb 2025 13:57:45 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id 3D9B23003E1; Thu, 6 Feb 2025 14:57:44 +0100 (CET) Date: Thu, 6 Feb 2025 14:57:44 +0100 From: Peter Zijlstra To: Sebastian Andrzej Siewior Cc: Steven Rostedt , Joel Fernandes , Prakash Sangappa , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, Thomas Gleixner , Ankur Arora , Linus Torvalds , linux-mm@kvack.org, x86@kernel.org, Andrew Morton , luto@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, willy@infradead.org, mgorman@suse.de, jon.grimm@amd.com, bharata@amd.com, raghavendra.kt@amd.com, Boris Ostrovsky , Konrad Wilk , jgross@suse.com, Andrew.Cooper3@citrix.com, Vineeth Pillai , Suleiman Souhlal , Ingo Molnar , Mathieu Desnoyers , Clark Williams , daniel.wagner@suse.com, Joseph Salisbury , broonie@gmail.com Subject: Re: [RFC][PATCH 1/2] sched: Extended scheduler time slice Message-ID: <20250206135744.GQ7145@noisy.programming.kicks-ass.net> References: <9DA1FAE6-A008-4785-BDF9-541457E29807@joelfernandes.org> <20250204220418.35949317@gandalf.local.home> <20250205081635.397eacb0@gandalf.local.home> <20250206083039.0916ad24@gandalf.local.home> <20250206134408.lD_POjuG@linutronix.de> <20250206134859.GP7145@noisy.programming.kicks-ass.net> <20250206135353.i1tp4vDv@linutronix.de> 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=us-ascii Content-Disposition: inline In-Reply-To: <20250206135353.i1tp4vDv@linutronix.de> On Thu, Feb 06, 2025 at 02:53:53PM +0100, Sebastian Andrzej Siewior wrote: > On 2025-02-06 14:48:59 [+0100], Peter Zijlstra wrote: > > On Thu, Feb 06, 2025 at 02:44:08PM +0100, Sebastian Andrzej Siewior wrote: > > > SCHED_OTHER vs SCHED_OTHER after all. But please don't delay a wakeup of > > > SCHED_FIFO/ RR/ DL because of this LAZY hint. > > > > Thing will get delayed if interrupts are disabled or kernel has > > preemption disabled too. So as long as we ensure hint crap is of equal > > order, nothing cares if you do. > > > > If you can't tell the difference between task does hint crap in > > userspace and task is in the middle of syscall, you can't tell the > > difference. > > I can tell the difference if I see a trace where an interrupt fires, > performs a wakeup and the SCHED_OTHER task remains on CPU while the task > SCHED_FIFO task sits on the runqueue until a timer fires. Right, but so what? Same delay will happen if interrupt fires in the middle of a preempt_disable() region. Or if interrupt gets pending while interrupts are disabled, except your trace will not show that. Your worst case response time isn't affected. That's all that matters.