Gary-Hobson commented on issue #16740:
URL: https://github.com/apache/nuttx/issues/16740#issuecomment-3095870990
There is no data in the result, which may be because the function was not
executed or the execution time was too short, resulting in the timer not
sampling any valid data (or the timer was not triggered at all, which is almost
impossible)
Two memory blocks are required in gprof, one for recording the timer
sampling data and the other for the function call relationship data. Their
resolutions are modified by HISTFRACTION and HASHFRACTION respectively
(although it is possible, it is not recommended and may lead to incorrect
results)
It is recommended to test in QEMU first to check if the operation steps are
correct (or execute the provided demo in RP2040 to see if the output results
are correct)
Below are the steps and results of changing HISTFRACTION to 16 in the qemu
environment.
```
./tools/configure.sh nuttx/boards/arm/qemu/qemu-armv7a/configs/nsh
make -j32
```
Configuration changes:
```
+CONFIG_FS_TMPFS=y
+CONFIG_PROFILE_MINI=y
+CONFIG_SYSTEM_GPROF=y
```
nsh command：
```
cd /tmp
gprof start
hello
gprof stop
gprof dump /tmp/gprof.out
hexdump /tmp/gprof.out
```
demo:
```c
void my_delay(int s)
{
struct timespec delay = {
.tv_sec = s,
};
struct timespec now, except;
clock_systime_timespec(&now);
clock_timespec_add(&now, &delay, &except);
while (clock_timespec_compare(&now, &except) < 0)
{
clock_systime_timespec(&now);
}
}
void foo(void)
{
syslog(0, "foo() called\n");
my_delay(1);
}
int main(int argc, FAR char *argv[])
{
foo();
printf("Hello, World!!\n");
return 0;
}
```
file diff:
```
diff --git a/libs/libbuiltin/libgcc/profile.c
b/libs/libbuiltin/libgcc/profile.c
index ad8b37a2bb6..2277860aa6d 100644
--- a/libs/libbuiltin/libgcc/profile.c
+++ b/libs/libbuiltin/libgcc/profile.c
@@ -50,7 +50,7 @@
/* Fraction of text space to allocate for histogram counters here, 1/2 */
-#define HISTFRACTION 2
+#define HISTFRACTION 16
```
Output:
```shell
# HISTFRACTION = 16
arm-none-eabi-gprof nuttx/nuttx gmon.out -b
Flat profile:
Each sample counts as 0.001 seconds.
% cumulative self self total
time seconds seconds calls Ts/call Ts/call name
**37.04 0.75 0.75 arm_timer_interrupt
30.93 1.38 0.63 up_timer_initialize
12.37 1.63 0.25 up_idle
12.35 1.88 0.25 arm_timer_get_freq**
6.19 2.00 0.13 up_allocate_heap
1.09 2.02 0.02 up_ndelay
0.05 2.02 0.00 lib_rdflush_unlocked
granularity: each sample hit covers 32 byte(s) for 0.05% of 2.02 seconds
====================================
# HISTFRACTION = 2
arm-none-eabi-gprof nuttx/nuttx gmon.out -b
Flat profile:
Each sample counts as 0.001 seconds.
% cumulative self self total
time seconds seconds calls Ts/call Ts/call name
49.48 1.00 1.00 up_idle
49.38 2.00 1.00 arm_timer_get_freq
1.09 2.02 0.02 up_ndelay
0.05 2.02 0.00 nxsched_waitpid
granularity: each sample hit covers 4 byte(s) for 0.05% of 2.02 seconds
```
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