linux-kernel - Re: [PATCH v3 0/2] Reduce CPU consumption after panic

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Message-ID: <20250429221049.GG4439@noisy.programming.kicks-ass.net>
Date: Wed, 30 Apr 2025 00:10:49 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Carlos Bilbao <bilbao@...edu>
Cc: Andrew Morton <akpm@...ux-foundation.org>, carlos.bilbao@...nel.org,
	tglx@...utronix.de, seanjc@...gle.com, jan.glauber@...il.com,
	pmladek@...e.com, jani.nikula@...el.com,
	linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
	takakura@...inux.co.jp, john.ogness@...utronix.de, x86@...nel.org
Subject: Re: [PATCH v3 0/2] Reduce CPU consumption after panic

On Tue, Apr 29, 2025 at 03:32:56PM -0500, Carlos Bilbao wrote:

> Yes, the machine is effectively dead, but as things stand today,
> it's still drawing resources unnecessarily.
> 
> Who cares? An example, as mentioned in the cover letter, is Linux running

Ah, see, I didn't have no cover letter, only akpm's reply.

> in VMs. Imagine a scenario where customers are billed based on CPU usage --
> having panicked VMs spinning in useless loops wastes their money. In shared
> envs, those wasted cycles could be used by other processes/VMs. But this
> is as much about the cloud as it is for laptops/embedded/anywhere -- Linux
> should avoid wasting resources wherever possible.

So I don't really buy the laptop and embedded case, people tend to look
at laptops when open, and get very impatient when they don't respond.
Embedded things really should have a watchdog.

Also, should you not be using panic_timeout to auto reboot your machine
in all these cases?

In any case, the VM nonsense, do they not have a virtual watchdog to
'reap' crashed VMs or something?