Messages in this thread | | | Date | Fri, 23 Oct 2009 12:37:46 +0200 | From | Ingo Molnar <> | Subject | Re: [performance problem] CONFIG_DYNAMIC_FTRACE: Increased kernel build times |
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* John Kacur <jkacur@redhat.com> wrote:
> 2009/10/23 Ingo Molnar <mingo@elte.hu> 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.
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