Re: tm_basic fixes

[GONZALEZ Laurent <laurent dot gonzalez at trango-systems dot com>]

On Tue, 01 Mar 2005 07:05:52 -0700
Gary Thomas <gary@mlbassoc.com> wrote:

> On Thu, 2005-02-24 at 15:13 +0100, GONZALEZ Laurent wrote:
> > hi list,
> > 
> > this patch removes an hardwired value to compute ns_per_system_clock 
> > variable and also restore the meaning of this variable (that should 
> > otherwise be renamed to us_per_system_clock). The test is now compliant 
> > with the definition of CYGNUM_HAL_RTC_NUMERATOR and CYGNUM_HAL_RTC_DENOMINATOR.
> > 
> > Moreover, it fixes the computation of clock interrupt cost. That's a 
> > good news for eCos because this cost is currently over-estimated.
> > 
> 
> Can you please explain your changes a bit more?
> 
> I agree with the change for CYGNUM_HAL_RTC_NUMERATOR, but the other
> two changes seem to cancel each other out.  When I tested this,
> before & after the patch, I got identical results so I'm a little
> interested in hearing more.
> 

First of all, it's good to hear that your figures did not change with the patch, it is intended to behave like that except for one of them: "Clock interrupt took xxx microseconds (xxx raw clock ticks)".

'tv1' is the mean value of tv[i]*1000, thus this value is scaled by a factor 1000. On the other hand, 'overhead' (from 'tv0') is not scaled, thus the substraction "tv1 -= overhead" does not compute the value we are looking for. See "show_times_detail" function where 'overhead' is substracted from 'delta' **before** scaling 'delta' 1000 times.

'ns_per_system_clock' is currently computed with an hardwired value instead of using CYGNUM_HAL_RTC_NUMERATOR. Moreover this value is 1/1000 of the value generally defined for CYGNUM_HAL_RTC_NUMERATOR. In other word 'ns_per_system_clock' is currently used in tm_basic code as if it were 'us_per_system_clock' !! Have a look at the following line:

    diag_printf("\nTiming complete - %d ms total\n\n", (int)((ticks*ns_per_system_clock)/1000));

Ticks is not scaled and we got ms from ns/1000 !! There is something wrong, isn't it ?

regards.

-- 
GONZALEZ Laurent
------------------------------------
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