[Questions] How to run 'perf top' on ARM to profile kernel functions with modules loaded

[Peter Zijlstra]

On Thu, 2010-11-11 at 09:17 +0000, Jamie Iles wrote:
> On Thu, Nov 11, 2010 at 03:52:07PM +0800, Ming Lei wrote:
> > 2010/11/11 Ming Lei <tom.leiming at gmail.com>:
> > > Hi,
> > >
> > > 'perf top' can't display any functions when modules are loaded on ARM.
> > 
> > Sorry, should be can't display any kernel functions when modules are loaded
> > on ARM.
> I've noticed this myself and I spent a bit of time looking into it last week 
> but didn't get too far. I did wonder if it was something to do with the map 
> fixups after loading the modules. If you look at the raw events after a perf 
> record with 'perf report -D' then the last module has a size that takes it to 
> 0xFFFFFFFF which overlaps with the rest of the kernel symbols.
> 
> On x86 it looks like the modules are loaded after the kernel image in VM 
> unlike ARM.

Order shouldn't matter, but that overlap is very likely what kills it.
That module size is buggy.