[LTP] questions about getrusage04

[LTP] questions about getrusage04

[Han Pingtian]

Hey,

I cannot understand why udelta/sdelta > "1000+(BIAS_MAX*factor_nr)" is a
problem. Could any expert give me a explain, please?

And looks like with this patch applied, it works well on powerpc:

diff --git a/testcases/kernel/syscalls/getrusage/getrusage04.c b/testcases/kernel/syscalls/getrusage/getrusage04.c
index 3640295..f118288 100644
--- a/testcases/kernel/syscalls/getrusage/getrusage04.c
+++ b/testcases/kernel/syscalls/getrusage/getrusage04.c
@@ -92,7 +92,7 @@ int main(int argc, char *argv[])
        if (msg != NULL)
                tst_brkm(TBROK, NULL, "OPTION PARSING ERROR - %s", msg);

-#if (__powerpc__) || (__powerpc64__) || (__s390__) || (__s390x__)
+#if (__s390__) || (__s390x__)
        tst_brkm(TCONF, NULL, "This test is not designed for current system");
 #endif

although the initial git comment said that "accuracy on powerpc 
and s390x systems is always 10ms".


Thanks in advance!


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Re: [LTP] questions about getrusage04

[Cyril Hrubis]

Hi!
> I cannot understand why udelta/sdelta > "1000+(BIAS_MAX*factor_nr)" is a
> problem. Could any expert give me a explain, please?

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.

> 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?

-- 
Cyril Hrubis
chrubis@suse.cz

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Re: [LTP] questions about getrusage04

[Han Pingtian]

On Mon, Dec 08, 2014 at 01:09:22PM +0100, Cyril Hrubis wrote:
> Hi!
> > I cannot understand why udelta/sdelta > "1000+(BIAS_MAX*factor_nr)" is a
> > problem. Could any expert give me a explain, please?
> 
> 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? 
> 
> > 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


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Re: [LTP] questions about getrusage04

[Cyril Hrubis]

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?

-- 
Cyril Hrubis
chrubis@suse.cz

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Re: [LTP] questions about getrusage04

[Han Pingtian]

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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