On Mon, Jun 02, 2014 at 11:57:40PM +1200, Christopher Gregory wrote:
> Hello,
>
> Well I have spent hours looking through the man pages on time(2), bash,
> and trying to modify the SBU calculation script that jhalf uses to work as
> a standalone to no avail.
>
> The script at:
>
> http://lists.linuxfromscratch.org/pipermail/alfs-discuss/2005-December/007441.html
>
> which has a few more features than the one on Bruce's SBU page:
>
> http://www.linuxfromscratch.org/~bdubbs/about.html
>
> is what I am using, with the program name modified accordingly.
>
> what I need is the value of Elapsed Time set to a variable so that I can
> divide it by the base_sbu value of bin-utils.
>
> I know that I can manually do this, but I really do need it to work in a
> script.
>
> The examples I have found on google are no help to me.
>
> There has to be a way to just pass the integer value of Elapsed Time to a
> variable without getting the frigging error that it is not an integer
> value.
>
> I know from the research that time outputs to stderr.
>
> I am NOT a scripter nor a very good programmer as I normally hate going
> around in endless circles going no where.
>
> Regards,
>
> Christopher.
>
My current scripts are a bit more involved than that. I still
calculate an SBU value, but only because I used to. In the
beginning, I stored $SECONDS.
Now, I use the following (actually, I have a lot of debug code as
well, and I've reformatted this slightly) -
km_start_SBU () {
# start the package's SBU timing from here, after it has
# been untarred
KM_DOING=$(date +%s.%N | awk '{ printf "%8.3f", $1 }')
}
km_end_SBU () {
# stop the timing : called from km_finish()
KM_DONE=$(date +%s.%N | awk '{ printf "%8.3f", $1 }')
}
km_calcSBU()
{
# calculate its SBU
# first calculate the elapsed time
KM_MYTIME=$(echo $KM_DOING $KM_DONE | awk '{ printf "%8.3f", $2-$1 }')
# if the SBU stamp exists, read it
if [ -f $KM_SBU ]; then
KM_SBUTIME=`tail -n 1 $KM_SBU | awk '{ print $NF}'`
# now set the sbu without a newline
KM_MYSBU=`echo $KM_MYTIME $KM_SBUTIME | \
awk '{ sbu = $1 / $2 ; printf("%3.1f",sbu) }'`
# minimum value is less than 0.1, not 0.0
if [ $KM_MYSBU = "0.0" ]; then
KM_MYSBU="less than 0.1"
fi
else
# set the SBU from first package (assumes a straight
# LFS build)
# and therefore own time is 1.0 SBU
echo $KM_MYTIME >$KM_SBU
KM_MYSBU="1.0"
fi
}
The key thing, as with any script, is to use the tools which are
available. In my case, I use awk for doing the maths.
I suggest that whole seconds are probably perfectly fine for most
usage of SBUs, there is always some variation between different runs
(and nowadays the variation has increased if I use the ondemand cpu
governor, so I've now stopped using that for measured builds).
A couple of other notes:
KM_MYSBU points to a file which holds the elapsed time in seconds
and decimals for 1.0 SBU, and the last line is what I use - after
the system is completed, I recalculate the SBU to see how it
compares to the SBU from the host system, so that recalculation uses
its own code to append a new line. That value is what I actually
use as the divisor when measuring packages for the book(s), but for
the measurements themselves I normally do a DESTDIR build and time
each step individually, then use a calculator.
All the KM_ and km_ prefixes are because _something_ broke when
bison got upgraded a year or so ago (i.e. bison would either not
compile, or its testsuite broke, I forget which). One of my
variables or functions had a name which the bison devs had decided
to use.
ĸen
--
Nanny Ogg usually went to bed early. After all, she was an old lady.
Sometimes she went to bed as early as 6 a.m.
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