From: Han Pingtian <hanpt@linux.vnet.ibm.com>
To: ltp-list@lists.sourceforge.net
Subject: Re: [LTP] questions about getrusage04
Date: Mon, 8 Dec 2014 21:52:50 +0800 [thread overview]
Message-ID: <20141208135250.GC3352@localhost.localdomain> (raw)
In-Reply-To: <20141208131931.GB13319@rei.suse.de>
On Mon, Dec 08, 2014 at 02:19:31PM +0100, Cyril Hrubis wrote:
> Hi!
> > > It tests timer precision for getrusage timers. If the timers are
> > > incremting by larger values than expected, something is wrong in kernel.
> > > The precision depends on CONFIG_HZ settings which is represented by the
> > > BIAS_MAX.
> > Where does the 1000 come from? If on a slow system, we need to increase
> > the "factor_nr", right?
>
> The factor is set to 1 and it shouldn't needed to change that.
>
> > > > And looks like with this patch applied, it works well on powerpc:
> > >
> > > Can you please share the output of the testcase on ppc and ppc64? What
> > > is the expected timer granularity there?
> > >
> > Looks like the granularity is 10000us:
> >
> > getrusage04 0 TINFO : Expected timers granularity is 10000 us
> > getrusage04 0 TINFO : Using 1 as multiply factor for max [us]time increment (1000+10000us)!
> > getrusage04 0 TINFO : utime: 56us; stime: 1192us
> > getrusage04 0 TINFO : utime: 56us; stime: 2009us
> > getrusage04 0 TINFO : utime: 56us; stime: 4233us
> > getrusage04 0 TINFO : utime: 1227us; stime: 5243us
> > getrusage04 0 TINFO : utime: 1227us; stime: 8541us
> > getrusage04 0 TINFO : utime: 2072us; stime: 8741us
> > getrusage04 0 TINFO : utime: 2602us; stime: 11169us
> > getrusage04 0 TINFO : utime: 2743us; stime: 11747us
> > getrusage04 0 TINFO : utime: 2948us; stime: 12790us
> > getrusage04 0 TINFO : utime: 2948us; stime: 18118us
> > getrusage04 0 TINFO : utime: 2948us; stime: 18596us
> > getrusage04 0 TINFO : utime: 4458us; stime: 20030us
> > getrusage04 0 TINFO : utime: 4458us; stime: 20244us
> > getrusage04 0 TINFO : utime: 4458us; stime: 23432us
> > getrusage04 0 TINFO : utime: 5412us; stime: 24650us
> > getrusage04 0 TINFO : utime: 5412us; stime: 27273us
> > getrusage04 0 TINFO : utime: 6125us; stime: 27909us
> > getrusage04 0 TINFO : utime: 6125us; stime: 27911us
> > getrusage04 0 TINFO : utime: 6125us; stime: 28111us
> > getrusage04 0 TINFO : utime: 6235us; stime: 28513us
> > getrusage04 0 TINFO : utime: 6235us; stime: 28750us
> > getrusage04 1 TPASS : Test Passed
>
> Hmm, this looks like the granularity of the timer is much smaller than
> 10000us and it varies greatly between measurements. Is this CONFIG_NO_HZ
> system?
Yes, looks like it is:
% grep CONFIG_NO_HZ /boot/config-2.6.32-504.el6.ppc64
CONFIG_NO_HZ=y
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prev parent reply other threads:[~2014-12-08 14:41 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-06 1:24 [LTP] questions about getrusage04 Han Pingtian
2014-12-08 12:09 ` Cyril Hrubis
2014-12-08 13:03 ` Han Pingtian
2014-12-08 13:19 ` Cyril Hrubis
2014-12-08 13:52 ` Han Pingtian [this message]
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