This describes to do profiling of user Trusted Applications with
The configuration option
CFG_TA_GPROF_SUPPORT=y enables OP-TEE to collect
profiling information from Trusted Applications running in user mode and
-pg. Once collected, the profiling data are formatted in the
gmon.out format and sent to
tee-supplicant via RPC, so they can be saved
to disk and later processed and displayed by the standard
- Build OP-TEE OS with
CFG_TA_GPROF_SUPPORT=y. You may also set
CFG_ULIBS_MCOUNT=yto instrument the user TA libraries contained in
- Build user TAs with
-pg, for instance enable:
CFG_TA_MCOUNT=yto instrument whole user TA. Note that instrumented TAs have a larger
.bsssection. The memory overhead is 1.36 times the
.textsize for 32-bit TAs, and 1.77 times for 64-bit ones (refer to the TA linker script for details:
- Run the application normally. When the last session exits,
tee-supplicantwill write profiling data to
/tmp/gmon-<ta_uuid>.out. If the file already exists, a number is appended, such as:
- Run gprof on the TA ELF file and profiling output:
gprof <ta_uuid>.elf gmon-<ta_uuid>.out
Part of the profiling is implemented in libutee. Another part is done in the TEE
core by a pseudo-TA (
core/arch/arm/sta/gprof.c). Two types of data are
- Call graph information
- When TA source files are compiled with the -pg switch, the compiler generates extra code into each function prologue to call the instrumentation entry point (
_mcountdepending on the architecture). Each time an instrumented function is called, libutee records a pair of program counters (one is the caller and the other one is the callee) as well as the number of times this specific arc of the call graph has been invoked.
- PC distribution over time
- When an instrumented TA starts, libutee calls the pseudo-TA to start PC sampling for the current session. Sampling data are written into the user-space buffer directly by the TEE core.
- Whenever the TA execution is interrupted, the TEE core records the current program counter value and builds a histogram of program locations (i.e., relative amount of time spent for each value of the PC). This is later used by the gprof tool to derive the time spent in each function. The sampling rate, which is assumed to be roughly constant, is computed by keeping track of the time spent executing user TA code and dividing the number of interrupts by the total time.
- The profiling buffer into which call graph and sampling data are recorded is allocated in the TA’s
.bsssection. Some space is reserved by the linker script, only when the TA is instrumented.