Messages in this thread | | | Subject | Re: [performance problem] CONFIG_DYNAMIC_FTRACE: Increased kernel build times | From | Steven Rostedt <> | Date | Fri, 23 Oct 2009 09:18:51 -0400 |
| |
On Fri, 2009-10-23 at 09:45 +0200, Ingo Molnar 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.
Yeah, I know this is quite a hit, and to fix this is on my todo list. What I plan on doing is checking if libelf is installed, and if it is, then doing a C program that does the linking and checking. If not, it defaults back to the perl code.
But I'm bug hunting right now, and that takes a higher priority.
-- Steve
| |