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 400CD34A30F for ; Fri, 5 Sep 2025 11:47:47 +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=1757072869; cv=none; b=qJKYXNvfMwxDDcarx3+FGCl4Huea4yaVHU6WmppxDrYoXqRoy/ARWDIWgCDL3bkaFK98hYlcD6ppPlpYVGy4TfdW1gN+mhvaeqjd+1Nhh4MzdbeAQ2erYUeVNIvwEIrB8GZCfkrs6J7XRl2s59jyT48EeAAl0PlhLvBrxB9HGMM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757072869; c=relaxed/simple; bh=FdU77GPJOYxh9ocYPZ2SLosHzgjN3maiq6j1EqF+Mmw=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=KelOOu+9tK4CSp4Bmz+qvEzNSstIrfQIdJTMLQBFI+ceaA42tmvf2a0yX1lwmZ8cwd/YofZ+0jpFS18mUXrn+gi8rmER+AeW6NtQtazYX1KG7bgW/3PyoKrIA54GIn6ipMxq3/QtDRyXGgGJOmh0Yn/fuTR8M7xqcebL/Bom3yo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=PMZ3qS4S; 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="PMZ3qS4S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 788E7C4CEF1; Fri, 5 Sep 2025 11:47:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1757072867; bh=FdU77GPJOYxh9ocYPZ2SLosHzgjN3maiq6j1EqF+Mmw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=PMZ3qS4SFYO4hBy0FiCKO5p7W8eTE5WHvmHyXftn3QsS9JkfyU/xmmVnxtd8DEIvL OFOoMJwqRYNfs6FOsh0JHeop0nRTAwNsBGjgnn+k8TmarQ+7QvB2ra7HUhwDZOT6jC jvbNgAKBqjdeTUSR/oIVxgvfXnnMU+6l+xE5FWGvXLbJTDwT0z7b8G9XmbgsJg6hZ+ HGeW53YkUU1yZcNsXLIF0hl2dxt5AsCP3RR1UpQVSiZ/DOIe+A7Cw4KkeSpJ0BVJgG W8Ps9CqLaYftc96Di/svVwUJ6+I5YkXxoosiwRwXU5dQnonowBlcVmZ5pXl9xfCz9u gkDzVBlvEKb+w== Date: Fri, 5 Sep 2025 13:47:44 +0200 From: Frederic Weisbecker To: "Christoph Lameter (Ampere)" Cc: Adam Li , anna-maria@linutronix.de, tglx@linutronix.de, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, vschneid@redhat.com, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, linux-kernel@vger.kernel.org, patches@amperecomputing.com Subject: Re: [PATCH RESEND 1/2] tick/nohz: Fix wrong NOHZ idle CPU state Message-ID: References: <20250821042707.62993-1-adamli@os.amperecomputing.com> <20250821042707.62993-2-adamli@os.amperecomputing.com> <6f14ff5c-cddb-f450-b4bb-fcc995b5ce5b@gentwo.org> 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: <6f14ff5c-cddb-f450-b4bb-fcc995b5ce5b@gentwo.org> Le Thu, Sep 04, 2025 at 09:10:29AM -0700, Christoph Lameter (Ampere) a écrit : > On Thu, 4 Sep 2025, Frederic Weisbecker wrote: > > > The current state is indeed broken and some people have already tried to fix it. > > The thing is nohz_full don't want dynamic isolation because it is deemed to run a > > single task. Therefore those tasks must be placed manually in order not to break > > isolation guarantees by accident. > > > > In fact nohz_full doesn't make much sense without isolcpus (or isolated cpuset > > v2 partitions) and I even intend to make nohz_full depend on domain isolation > > in the long term. > > I have never used isolcpus with nohz_full. AFAICT isolcpus is depreciated > and cpusets are unnecessary complex overhead. isolcpus for domain isolation is indeed in the way for long term deprecation and the only replacement possible is cpuset, which overhead is only visible on partition creation and update. We could argue on the interface, the point is that nohz_full doesn't make sense without domain isolation. Thanks. -- Frederic Weisbecker SUSE Labs