linux-kernel - /proc/uptime idle counter remains at 0

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Message-ID: <alpine.LSU.2.00.0905090957490.27646@fbirervta.pbzchgretzou.qr>
Date:	Sat, 9 May 2009 10:05:57 +0200 (CEST)
From:	Jan Engelhardt <jengelh@...ozas.de>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	michael@...neidae.co.uk
Subject: /proc/uptime idle counter remains at 0

Hi,


starting from v2.6.28-4930-g79741dd lasting thru at least v2.6.29.1,
the second field of /proc/uptime always shows 0.00. This happens for
both the typical i386 (my case) and on an ARM (according to Michael,
cc'ed).

>From the commit log of 79741dd:

	"""The cpu time spent by the idle process actually doing
	something is currently accounted as idle time. This is plain
	wrong, the architectures that support VIRT_CPU_ACCOUNTING=y
	can do better: distinguish between the time spent doing
	nothing and the time spent by idle doing work. The first is
	accounted with account_idle_time and the second with
	account_system_time."""

Citing Michael from our irc conversation:

	"""the writer[committer] [says] that [the] idle process time
	isn't really idle time ... but that's all that /proc/uptime
	looks at. I guess fs/proc/uptime.c needs to catch up."""

So, were the updates to uptime.c missed, or do we now live on with
/proc/uptime constantly having 0?



Jan
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