2009/10/23 Ingo Molnar <[email protected]> wrote:
>
> Steve,
>
> i did an 64-bit allyesconfig build test (with debug_info disabled), with
> and without CONFIG_DYNAMIC_FTRACE set.
>
> The build time results are:
>
> ?-CONFIG_DYNAMIC_FTRACE: ? 266.30
> ?+CONFIG_DYNAMIC_FTRACE: ? 296.07 (+11.2%)
>
> So we get more than 10% build time overhead.
>
> That's quite high - higher than what i remember having measured
> originally when the first iteration of the mcount code went in.
>
> This extra overhead comes from the mcount post-processing script
> (scripts/recordmcount.pl) that runs objcopy as well and is written in
> Perl. I think this whole angle needs to be improved - 10% is way too
> high of a price to pay.
Hi Ingo, do you still have the profiling data to share with us?
Was the problem more in objcopy / objdump, rather than in the perl script
itself?
Thanks
John
* John Kacur <[email protected]> wrote:
> 2009/10/23 Ingo Molnar <[email protected]> wrote:
> >
> > Steve,
> >
> > i did an 64-bit allyesconfig build test (with debug_info disabled), with
> > and without CONFIG_DYNAMIC_FTRACE set.
> >
> > The build time results are:
> >
> > ?-CONFIG_DYNAMIC_FTRACE: ? 266.30
> > ?+CONFIG_DYNAMIC_FTRACE: ? 296.07 (+11.2%)
> >
> > So we get more than 10% build time overhead.
> >
> > That's quite high - higher than what i remember having measured
> > originally when the first iteration of the mcount code went in.
> >
> > This extra overhead comes from the mcount post-processing script
> > (scripts/recordmcount.pl) that runs objcopy as well and is written in
> > Perl. I think this whole angle needs to be improved - 10% is way too
> > high of a price to pay.
>
> Hi Ingo, do you still have the profiling data to share with us? [...]
no finegrained info - i did a perf stat run.
> [...] Was the problem more in objcopy / objdump, rather than in the
> perl script itself?
in top i saw perl pop up most of the time, that's where i'd suspect a
good portion of the overhead.
Ingo