From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 9DF2E1863F for ; Fri, 17 May 2024 14:50:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715957459; cv=none; b=gbD7KsPyaiNFqhHQd/k6k5uDwzV2HAmCTvOS0VNAGF7fgd6DrYHKzKTVx5Ah7lnU+EfQOrI1VLeXlEvFksiPLGivgRgkXZUoPifgSE43jsJL9nKSNWAgxC6pHEumF9IzKxN/DJ2jqhCBFkDYxp2mXASEBpgMQ/bENrtANuIKkL0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715957459; c=relaxed/simple; bh=/3Ff205MN8HPJmBvMpwpWRFGY7yUTT9Pn5wmoEEM/gw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=ULZOV2AbCa1XzUhq6mVRLRUFB4wUJCmlJak13RzpjHb9RTArFCOjCO9Fu5lo21sjjRXG7aDPnT33bRGUu2sAw5KCLmjG8ic2BXQgd/h2xl1Ia0SSo5s8WsQA5fgt4opUEi7WKtpkmKA6PBrX/cqUhdE6IhWRngEnECBPmuUD3NY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=NCd0e5Wk; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="NCd0e5Wk" Received: by smtp.kernel.org (Postfix) with ESMTPSA id ED950C2BD10; Fri, 17 May 2024 14:50:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715957459; bh=/3Ff205MN8HPJmBvMpwpWRFGY7yUTT9Pn5wmoEEM/gw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=NCd0e5WkPiDFIR4LEwBHnb56CyyWxfk3T9IhBesuNmMwENf5/QRX7LAf0BTUkUR2u IubphLQ0cjXXDv+v9Y9ok5to/pPGfUbLCT8vAlx+BL+QseFMOPa7oCu86VmFcjQcBe P92YYEHxRQ4joIJNZZFgAibVQFrZooxFnNGztZF30hom2deOHhJ4wzNgOkCNxZY7s8 qK16zwb4hqrKT2+RCaZ6pvZAo1Dw8BT4RMP2ls1XIlj7B2K+4+pO6AfMayDB6fnv9t 1I3dUfkGolM0i2fhPRNL3ZxraygAIPuTSqQ6GM98jx9cKFKnQPNV9gQaiBLyHaSeww jfFa4hrrpw/BQ== Date: Fri, 17 May 2024 16:50:56 +0200 From: Frederic Weisbecker To: Peter Zijlstra 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: 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> <20240516175321.GN22557@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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20240516175321.GN22557@noisy.programming.kicks-ass.net> Le Thu, May 16, 2024 at 07:53:21PM +0200, Peter Zijlstra a écrit : > 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. Ok, I'll try something. Thanks.