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Message-ID: <20090212015503.GA4697@nowhere>
Date: Thu, 12 Feb 2009 02:55:04 +0100
From: Frederic Weisbecker <fweisbec@...il.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
Andrew Morton <akpm@...ux-foundation.org>,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
linuxppc-dev@...abs.org, Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 0/7][RFC] function graph tracer port to PowerPC
On Wed, Feb 11, 2009 at 08:10:51PM -0500, Steven Rostedt wrote:
>
> The following set of patches are RFC and not for inclusion
> (unless everyone is fine with them as is).
>
> This is the port to PowerPC of the function graph tracer that was written
> by Frederic Weisbecker for the x86 architecture. It is broken up
> into a series of logical steps.
>
> 1) get generic code ready for other archs
> 2) get PowerPC 64-bit working with just static function tracing
> 3) get PowerPC 64-bit working with dynamic function tracing
> 4) get PowerPC 32-bit working with just static function tracing
> 5) get PowerPC 32-bit working with dynamic function tracing
>
> (with some clean ups in between)
>
Thanks a lot Steven!
I'm sad to not having a Power Pc to test it...
> The function graph tracer not only traces the start of a function
> (uses the function tracer part for that) but also uses the kprobes
> trick to replace the return address with a hook to trace the exit
> of the function. These hooks are generic in that other tracers
> can also use them. But the function graph tracer itself is very
> powerful. Simply doing the following:
>
> # echo function_graph > /debug/tracing/current_tracer
> # cat /debug/tracing/trace
>
> # tracer: function_graph
> #
> # CPU OVERHEAD/DURATION FUNCTION CALLS
> # | | | | | | |
> ------------------------------------------
> 0) less-2228 => cat-2229
> ------------------------------------------
>
> 0) | .__do_fault() {
> 0) | .filemap_fault() {
> 0) | .find_lock_page() {
> 0) | .find_get_page() {
> 0) 3.168 us | .__rcu_read_lock();
> 0) 2.704 us | .__rcu_read_unlock();
> 0) + 14.640 us | }
> 0) + 20.112 us | }
> 0) + 26.464 us | }
> 0) 2.912 us | ._spin_lock();
> 0) 2.656 us | .page_add_file_rmap();
> 0) | .update_mmu_cache() {
> 0) | .hash_preload() {
> 0) 2.368 us | .get_slice_psize();
> 0) 2.752 us | .hash_page_do_lazy_icache();
> 0) 3.568 us | .native_hpte_insert();
> 0) + 19.680 us | }
> 0) + 24.960 us | }
> 0) 2.336 us | ._spin_unlock();
> 0) | .unlock_page() {
> 0) 2.688 us | .page_waitqueue();
> 0) 2.608 us | .__wake_up_bit();
> 0) + 12.912 us | }
> 0) ! 351.776 us | }
> 0) ! 357.392 us | }
> 0) 3.040 us | .up_read();
> 0) | .compat_sys_ioctl() {
> 0) 3.024 us | .fget_light();
> 0) | .tty_compat_ioctl() {
> 0) 2.704 us | .tty_paranoia_check();
> 0) | .tty_ldisc_ref_wait() {
> 0) | .tty_ldisc_try() {
> 0) 2.880 us | ._spin_lock_irqsave();
> 0) 2.928 us | ._spin_unlock_irqrestore();
> 0) + 13.776 us | }
> 0) + 19.424 us | }
>
> [...]
>
> As you can see, it gives a nice call trace of the functions being called
> at run time, as well as a time stamp of how much time the function
> took to execute.
>
> Adding dynamic tracing to the mix, we can trace a single function:
>
> # echo .do_fork > /debug/tracing/set_graph_function
> # echo function_graph > /debug/tracing/current_tracer
> # cat /debug/tracing/trace
>
> # tracer: function_graph
> #
> # CPU OVERHEAD/DURATION FUNCTION CALLS
> # | | | | | | |
> 1) | .do_fork() {
> 1) | .copy_process() {
> 1) | .prepare_to_copy() {
> 1) 2.944 us | .flush_fp_to_thread();
> 1) 2.800 us | .flush_altivec_to_thread();
> 1) 2.608 us | .flush_vsx_to_thread();
> 1) + 19.184 us | }
> 1) | .kmem_cache_alloc() {
> 1) 2.464 us | .slab_should_failslab();
> 1) 8.304 us | }
> 1) | .alloc_thread_info() {
> 1) | .kmem_cache_alloc() {
> 1) 2.512 us | .slab_should_failslab();
> 1) 8.224 us | }
> 1) + 13.344 us | }
> 1) 7.584 us | .arch_dup_task_struct();
> 1) | .copy_creds() {
> 1) 2.736 us | .__mutex_init();
> 1) | .prepare_creds() {
> 1) | .kmem_cache_alloc() {
> 1) 2.640 us | .slab_should_failslab();
> 1) 8.368 us | }
>
> [...]
>
>
> Note, the '.' in the '.do_fork' is a PowerPC64 thing. PowerPC32 and
> other archs just need to do 'do_fork', without the dot.
>
>
> The following patches are in:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
>
> branch: rfc/ppc/ftrace
>
>
> Steven Rostedt (7):
> tracing/function-graph-tracer: make arch generic push pop functions
> powerpc64: port of the function graph tracer
> powerpc64, tracing: add function graph tracer with dynamic tracing
> powerpc64, ftrace: save toc only on modules for function graph
> powerpc32, ftrace: save and restore mcount regs with macro
> powerpc32, ftrace: port function graph tracer to ppc32, static only
> powerpc32, ftrace: dynamic function graph tracer
>
> ----
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/ftrace.h | 39 ++++++++++-
> arch/powerpc/kernel/Makefile | 9 +-
> arch/powerpc/kernel/entry_32.S | 115 ++++++++++++++---------------
> arch/powerpc/kernel/entry_64.S | 89 +++++++++++++++++++++-
> arch/powerpc/kernel/ftrace.c | 135 ++++++++++++++++++++++++++++++++--
> arch/powerpc/kernel/process.c | 16 ++++
> arch/powerpc/kernel/vmlinux.lds.S | 1 +
> arch/x86/include/asm/ftrace.h | 25 ------
> arch/x86/kernel/ftrace.c | 75 +------------------
> include/linux/ftrace.h | 24 ++++++
> kernel/trace/trace_functions_graph.c | 75 +++++++++++++++++++
> 12 files changed, 428 insertions(+), 176 deletions(-)
> --
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