Using apcs frame layout

[Anton Kozlov]

Hi,

yes, unwind works because whole java uses standart layout. Perf
captures stacktraces in kernel mode, where no dwarf info available, and
standart layout assumed.

GCC forced to generate standart layout for hotspot, -fno-omit-frame
-pointer used on linux platform and amd64 cpu
(hotspot/make/solaris/makefiles/amd64.make,
hotspot/make/linux/makefiles/gcc.make).
JNI code have to be compiled with -fno-omit-frame-pointer too,
otherwise perf can't catch proper stacktrace. 
And java code uses standart layout.

So, for java, dwarf info isn't used at all.

Thanks,
Anton

On Wed, 2016-03-30 at 09:02 +0100, Andrew Haley wrote:
> On 29/03/16 18:48, Anton Kozlov wrote:
> > Sorry, not quite undestand you, what can we do? Add apcs layout
> > option?
> 
> I'm not sure exactly.  Let me ask a clarifying question: with
> x86-64, how do flame graphs work with Java?  Is it that Java
> uses the standard frame layout throughout?  But x86-64 doesn't
> use a standard frame layout in GCC.  It uses DWARF unwinder
> data.  So how does x86-64 OpenJDK work with flame graphs?
> 
> Andrew.
> 
>