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sandbox: Add gprof profiling support

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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>
This commit is contained in:
Simon Glass
2026-01-01 10:51:23 -07:00
parent 30dd519510
commit e77755ed85
3 changed files with 48 additions and 0 deletions
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4
arch/sandbox/config.mk
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@@ -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

4
config.mk
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@@ -63,6 +63,10 @@ ifdef FTRACE
PLATFORM_CPPFLAGS += -finstrument-functions -DFTRACE
endif
ifdef GPROF
PLATFORM_CPPFLAGS += -pg
endif
#########################################################################
RELFLAGS := $(PLATFORM_RELFLAGS)

40
doc/develop/trace.rst
View File

@@ -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
-----------