linux-kernel - Re: [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle cpus

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Message-ID: <20160321214935.GF6344@twins.programming.kicks-ass.net>
Date:	Mon, 21 Mar 2016 22:49:35 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Chris Metcalf <cmetcalf@...lanox.com>
Cc:	Russell King <linux@....linux.org.uk>,
	Thomas Gleixner <tglx@...utronix.de>,
	Aaron Tomlin <atomlin@...hat.com>,
	Ingo Molnar <mingo@...hat.com>, Andrew Morton <akpm@...l.org>,
	Daniel Thompson <daniel.thompson@...aro.org>, x86@...nel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org, "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH v2 4/4] nmi_backtrace: generate one-line reports for idle
 cpus

On Wed, Mar 16, 2016 at 01:02:13PM -0400, Chris Metcalf wrote:
> When doing an nmi backtrace of many cores, most of which are idle,
> the output is a little overwhelming and very uninformative.  Suppress
> messages for cpus that are idling when they are interrupted and just
> emit one line, "NMI backtrace for N skipped: idling at pc 0xNNN".

This is still 100+ lines on a modern system, but better than the many
many thousands it would otherwise generate.

> We do this by grouping all the cpuidle code together into a new
> .cpuidle.text section, and then checking the address of the
> interrupted PC to see if it lies within that section.
> 
> Signed-off-by: Chris Metcalf <cmetcalf@...lanox.com>

Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Tested-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Please Cc Rafael on the next posting.