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 0D4CC16DC28 for ; Tue, 29 Apr 2025 20:39:42 +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=1745959183; cv=none; b=rLOzbrBtDh6KbCIUhNss0RoOZPzrngGNcNXANuF+tWgR+4q3y7rOA6EO3BbfdKjYkP/U5i8TL2MBJxEJn3Pkq7qcpqWrdO9zs6fFANm1+RPBbIf2Z21pfCBMiOu9i/Qgsby8jYrl1Snv9oapj6l4q7wRAieuvdtIho7qLaeNvRw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1745959183; c=relaxed/simple; bh=ZUs1RHwHkXEDQaSSYSd7+zpQpA0rtzZG37moqeP6BgI=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=ZmmMC/l0DJkODy+ptAY4E0TdkOowO1S/+OWa6r2H6tUDxCyQjJMqPfYNcJ0KFDO03FosZHv6UJklqgQKihRmDm0ToOPN31q+qy9O8CQHXw7tB61Beri73PihDydD2I7CW5Mdrhoq58IX6DqKvfBpnRbRGjqlBGIQXRZQ/06xYI0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=Db85jYIY; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="Db85jYIY" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 21D2EC4CEE3; Tue, 29 Apr 2025 20:39:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1745959182; bh=ZUs1RHwHkXEDQaSSYSd7+zpQpA0rtzZG37moqeP6BgI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Db85jYIYlgnYWhOhbPdxOdhOYAk44JDS5INdAgfGPeKGZsdACQHSaE89HLKwTcv7Y J/4I7qlFuUDQ6PTpmIXCV9OMNBwbXxBbHaRDIgF5uWgPzPnaxlf+AImwzJBgyrojIz DQ4XjELZvP1ZPlSuL3DOFZ3+WHBlEUW9sRiyNEwU= Date: Tue, 29 Apr 2025 13:39:41 -0700 From: Andrew Morton To: carlos.bilbao@kernel.org Cc: tglx@linutronix.de, seanjc@google.com, jan.glauber@gmail.com, bilbao@vt.edu, pmladek@suse.com, jani.nikula@intel.com, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, takakura@valinux.co.jp, john.ogness@linutronix.de, x86@kernel.org Subject: Re: [PATCH v3 0/2] Reduce CPU consumption after panic Message-Id: <20250429133941.063544bb4731df0ef802440c@linux-foundation.org> In-Reply-To: <20250429150638.1446781-1-carlos.bilbao@kernel.org> References: <20250429150638.1446781-1-carlos.bilbao@kernel.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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-Transfer-Encoding: 7bit (cc more x86 people) On Tue, 29 Apr 2025 10:06:36 -0500 carlos.bilbao@kernel.org wrote: > From: Carlos Bilbao > > Provide a priority-based mechanism to set the behavior of the kernel at > the post-panic stage -- the current default is a waste of CPU except for > cases with console that generate insightful output. > > In v1 cover letter [1], I illustrated the potential to reduce unnecessary > CPU resources with an experiment with VMs, reducing more than 70% of CPU > usage. The main delta of v2 [2] was that, instead of a weak function that > archs can overwrite, we provided a flexible priority-based mechanism > (following suggestions by Sean Christopherson), panic_set_handling(). > An effect of this is that the blinky light will never again occur on any x86, I think? I don't know what might the effects of changing such longstanding behavior. Also, why was the `priority' feature added? It has no effect in this patchset.