linux-kernel - Re: Wakeup latency measured with SCHED

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Message-ID: <5093D8DE.70505@meduna.org>
Date:	Fri, 02 Nov 2012 15:29:50 +0100
From:	Stanislav Meduna <stano@...una.org>
To:	"linux-rt-users@...r.kernel.org" <linux-rt-users@...r.kernel.org>
CC:	shawn.guo@...aro.org, linux@....linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: Wakeup latency measured with SCHED_TRACER depends on HZ

On 31.10.2012 22:41, Stanislav Meduna wrote:

> on an embedded platform using a Freescale i.MX28 ARM processor
> I am experiencing a strange phenomenon - the latencies reported
> are dependent of HZ

OK, the problem is that the MXS platform does not setup
the scheduler clock so the scheduler only sees the HZ one.

The patch in attach fixes this. I can only test the MX28 part -
I don't have any timrot_is_v1() (MX23) hardware and I don't
know whether a source that wraps after ~2 seconds is OK at all.

Please Cc: when replying, I am not subscribed to linux-kernel
(only to linux-rt-users).

Regards
-- 
                                      Stano

View attachment "0001-Setup-scheduler-clock-for-MXS.patch" of type "text/plain" (1512 bytes)