From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 58141C02194 for ; Thu, 6 Feb 2025 13:58:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id C5E84280005; Thu, 6 Feb 2025 08:58:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id C0DC6280002; Thu, 6 Feb 2025 08:58:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id AD517280005; Thu, 6 Feb 2025 08:58:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 8E838280002 for ; Thu, 6 Feb 2025 08:58:08 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 0F798161214 for ; Thu, 6 Feb 2025 13:57:57 +0000 (UTC) X-FDA: 83089673394.30.E3F9BBC Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf19.hostedemail.com (Postfix) with ESMTP id 0F9841A004E for ; Thu, 6 Feb 2025 13:57:54 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=qFAwRwU9; spf=none (imf19.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1738850275; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=aS8G2mLVXo/L1oMuqtZDMH9m5wICqaE0EgdSFqltFMQ=; b=N6iE/0hHmNiioCJgCzXqmT2N6Amc/i2qvjP40b/7Pykbk5q+zw5GFtUa07X6iaZscOO1HQ xkkMOFuEc2Qgjmzfhoamq7CcJPLcq8HgP4EvHIMU66+G8wXjgdrgnl71BlXdiLNV1cYQ90 l/ZX/9ThyY5yeRdrmfLmF48P8EgIdNQ= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=qFAwRwU9; spf=none (imf19.hostedemail.com: domain of peterz@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=peterz@infradead.org; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1738850275; a=rsa-sha256; cv=none; b=pyqrnhn+9+1i05nozp5ptm7b1syFokCVnwBXEJ1L3TVeBd+jymAC1qF2orO1zl8v8y4Akd k0J4WrDBn4xvXUJfj8X/vXOdDtHnE5YHsiL4wyoKKAti0bzPGlYENGpOIp2pmA+hTVCzsl 0dQdhYrjmrS5MsbJXXJTfgYOcqnVpeM= 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250206135353.i1tp4vDv@linutronix.de> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 0F9841A004E X-Stat-Signature: nm1a3g8zqoj79ca7w3c7sc7aepzeji6i X-HE-Tag: 1738850274-631702 X-HE-Meta: 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 PLUlBJHK uYikWoPW/Sfo6xtqv8VhIUlAnp6YFRxrBXqSWr+vxP2sVV1/Ii0ku5SzlF/boel/PCXX5s44XtwPZF9rrVR7fynUFCSC8VqZD6zeXQawYHrVdIbrQKMaIKsAyviQE4EzIo2LVsoqpTQnxAluU/Z3rnwg2nWSTterjnQxnWHEkq0AbPBB7k6nP9tncPkHPADjVZBN0Kqs6pKpmUlSFYab0/gn7OKE4m1yMrLk/7xwDyQvYqHHKRAQjWoVAsbI6zd7l6oJQM5QPTxv30ik= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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.