From: Simon Glass <simon.glass@canonical.com> Add a GPROF=1 build option to enable gprof profiling for sandbox. This adds the -pg flag to both compiler and linker when GPROF=1 is set, following the same pattern as the existing FTRACE option. Usage: make GPROF=1 sandbox_defconfig all ./u-boot -T -c "ut dm" ... gprof u-boot gmon.out Co-developed-by: Claude <noreply@anthropic.com> Signed-off-by: Simon Glass <simon.glass@canonical.com> --- (no changes since v1) arch/sandbox/config.mk | 4 ++++ config.mk | 4 ++++ doc/develop/trace.rst | 40 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 48 insertions(+) diff --git a/arch/sandbox/config.mk b/arch/sandbox/config.mk index b92c259d2e3..92bac07963e 100644 --- a/arch/sandbox/config.mk +++ b/arch/sandbox/config.mk @@ -10,6 +10,10 @@ PLATFORM_LIBS += -L$(GCC_LIB_DIR) -lbacktrace endif PLATFORM_LIBS += -lrt +ifdef GPROF +PLATFORM_LIBS += -pg +endif + SDL_CONFIG ?= sdl2-config # Define this to avoid linking with SDL, which requires SDL libraries diff --git a/config.mk b/config.mk index e294be2a4c4..82fdbf3b4f6 100644 --- a/config.mk +++ b/config.mk @@ -63,6 +63,10 @@ ifdef FTRACE PLATFORM_CPPFLAGS += -finstrument-functions -DFTRACE endif +ifdef GPROF +PLATFORM_CPPFLAGS += -pg +endif + ######################################################################### RELFLAGS := $(PLATFORM_RELFLAGS) diff --git a/doc/develop/trace.rst b/doc/develop/trace.rst index d3c8628d124..d3393244658 100644 --- a/doc/develop/trace.rst +++ b/doc/develop/trace.rst @@ -491,6 +491,46 @@ can dramatically increase the size of the trace output as well as the execution time. +Wall-clock Profiling with gprof (Sandbox) +----------------------------------------- + +For sandbox builds, an alternative to U-Boot's internal tracing is to use +the standard GNU gprof profiler. This provides wall-clock profiling with +less overhead than function instrumentation, and produces output that can +be analysed with standard tools. + +To build sandbox with gprof support:: + + make GPROF=1 O=/tmp/b/sandbox sandbox_defconfig + make GPROF=1 O=/tmp/b/sandbox + +Then run U-Boot. A `gmon.out` file is created in the current directory when +the program exits:: + + cd /tmp/b/sandbox + ./u-boot -T -c "ut dm dm_test_rtc_set_get" + +Analyse the results with gprof:: + + gprof u-boot gmon.out | less + +This shows a flat profile (functions sorted by time) and a call graph. The +flat profile shows which functions consume the most CPU time:: + + % cumulative self self total + time seconds seconds calls ms/call ms/call name + 29.41 0.05 0.05 36922 0.00 0.00 memset + 17.65 0.08 0.03 read_uleb128 + 11.76 0.10 0.02 328472 0.00 0.00 string + ... + +The call graph shows the call hierarchy and time spent in each call chain. + +Note that gprof measures CPU time, not wall-clock time, so I/O wait time is +not captured. For boot-time optimisation where I/O is significant, use +bootstage or the internal trace system instead. + + Future Work ----------- -- 2.43.0