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 19B2014D457 for ; Thu, 16 May 2024 17:53:26 +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=1715882008; cv=none; b=uD5ihQCcjwMOibIAtOerhBg0wAL+knvaTYJmTd6QupmGyFoyCixzIXma162V+7Tea7OChc36WuacMlXJHhvUD4z3m8FUTYfqU9AWjHU0wgHg3BfzAaXuwvDXu9VErJJTh9v3XNcStGfBJ3Mm2mntD0qKcbF7Pxlh1OTDWL3vSD4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715882008; c=relaxed/simple; bh=PXXsy1vuFtGyoNlHHSR8xTWBE0S55BXma7bKe4Je6ic=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=X1UPUbWvezM5uytA66SYGAqybkGM/Dyd0V5RFxS5tma0wBN9y00y874udKIpkKrX1zwbsjcfqE4BEAWlK5Voa0Mw5taqD6u/xN7wOcqKwCGEryFwsLQBsHepvFbv/kIwhZzYElQHBPofElveGg++0bLJ5ADDNkSQyX2aIbvByQs= 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=UvSuQdES; 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="UvSuQdES" 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=JZ8dIVPdliawbwUcKrUeitOAz8xKG5PgkXSZmGQa9D4=; b=UvSuQdESm81j8qVqZLrsfFXdHd gRs10BA65Kv8cpXTTmuh9WepRZTt9KxErvu0Jqi5m8suw4U/j8GgY0DIRRqk8+5hlZ352vEG0AVSD G5LEIE0poHMWnIcdczG6gJUV2K3DG0o8kJNQdRefrW+PIHcogEhguQZaMaZXe5hY/jgr/4nLIWPvL Zg/DpFA04icWBk0qt1bS2umQr7HwLIeOx436DhKlpFxQ2D92KlHpfZpq+Q/hOXYaVVbMGmDlMpAiM YoMPNfQ4T2JdfeY/stDro9hPEDSwTckQ3I5nhG3PYIVmgG4K4ZuoAIIQKQPJd+4bMn12stg85TEXk GASg3Mfw==; Received: from j130084.upc-j.chello.nl ([24.132.130.84] helo=noisy.programming.kicks-ass.net) by casper.infradead.org with esmtpsa (Exim 4.97.1 #2 (Red Hat Linux)) id 1s7fIA-0000000C3mA-2EHl; Thu, 16 May 2024 17:53:22 +0000 Received: by noisy.programming.kicks-ass.net (Postfix, from userid 1000) id EFC3630068B; Thu, 16 May 2024 19:53:21 +0200 (CEST) Date: Thu, 16 May 2024 19:53:21 +0200 From: Peter Zijlstra To: Frederic Weisbecker Cc: Yun Levi , Joel Fernandes , Vineeth Pillai , Vincent Guittot , Dietmar Eggemann , anna-maria@linutronix.de, mingo@kernel.org, tglx@linutronix.de, Markus.Elfring@web.de, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4] time/tick-sched: idle load balancing when nohz_full cpu becomes idle. Message-ID: <20240516175321.GN22557@noisy.programming.kicks-ass.net> References: <20240516084911.GF22557@noisy.programming.kicks-ass.net> <20240516140003.GJ22557@noisy.programming.kicks-ass.net> <20240516144504.GL22557@noisy.programming.kicks-ass.net> <20240516151953.GM22557@noisy.programming.kicks-ass.net> 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-Disposition: inline In-Reply-To: On Thu, May 16, 2024 at 05:32:56PM +0200, Frederic Weisbecker wrote: > On Thu, May 16, 2024 at 05:19:53PM +0200, Peter Zijlstra wrote: > > Yes, but stronger, as long as the CPU is part of a load-balance domain, > > it must not disable the tick while running anything. > > > > that is, NOHZ_FULL must not become active unless it's running on a > > single CPU partition. > > I like the idea but I'm afraid to introduce regressions while doing so, > with people currently using nohz_full without proper partionning... There is no regression, if this is possible today it is utterly broken. This should never have been possible.