Messages in this thread | | | Date | Tue, 3 Feb 2009 16:31:39 +0100 | From | Ingo Molnar <> | Subject | Re: [PATCH 3/4] gcov: add gcov profiling infrastructure |
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* Peter Oberparleiter <oberpar@linux.vnet.ibm.com> wrote:
> From: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> > > Enable the use of GCC's coverage testing tool gcov [1] with the Linux > kernel. gcov may be useful for: > > * debugging (has this code been reached at all?) > * test improvement (how do I change my test to cover these lines?) > * minimizing kernel configurations (do I need this option if the > associated code is never run?) > > The profiling patch incorporates the following changes: > > * change kbuild to include profiling flags > * provide functions needed by profiling code > * present profiling data as files in debugfs > > Note that on some architectures, enabling gcc's profiling option > "-fprofile-arcs" for the entire kernel may trigger compile/link/ > run-time problems, some of which are caused by toolchain bugs and > others which require adjustment of architecture code. > > For this reason profiling the entire kernel is initially restricted > to those architectures for which it is known to work without changes. > This restriction can be lifted once an architecture has been tested > and found compatible with gcc's profiling. Profiling of single files > or directories is still available on all platforms (see config help > text). > > > [1] http://gcc.gnu.org/onlinedocs/gcc/Gcov.html > > Signed-off-by: Peter Oberparleiter <oberpar@linux.vnet.ibm.com> > --- > > Documentation/gcov.txt | 246 ++++++++++++++ > Documentation/kernel-parameters.txt | 7 > Makefile | 11 > arch/Kconfig | 1 > init/main.c | 8 > kernel/Makefile | 1 > kernel/gcov/Kconfig | 48 ++ > kernel/gcov/Makefile | 3 > kernel/gcov/base.c | 145 ++++++++ > kernel/gcov/fs.c | 620 ++++++++++++++++++++++++++++++++++++ > kernel/gcov/gcc_3_4.c | 419 ++++++++++++++++++++++++ > kernel/gcov/gcov.h | 128 +++++++ > scripts/Makefile.lib | 9 > 13 files changed, 1641 insertions(+), 5 deletions(-)
Nice tool - with one general observation: i'd really prefer if this was properly integrated with ftrace.
In particular the per object file controls are nice - those might be useful to seed ftrace filters as well.
So there's good synergy possible and we should reach that synergy before this goes upstream instead of putting it into a separate debugfs position with incompatible flags and concepts. Especially since user-space tools will pick up the gcov data so this gets hardcoded compatibility-wise very quickly and changing it after the fact will be harder.
Yes, it's more work and it means extending both the ftrace code and the gcov code - but it's very much worth it.
Ingo
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