Linux application profiling
Ideally, I need an application that will attach to a process and log periodic snapshots of:
- memory usage
- number of threads
- CPU usage
Well, in order to collect this type of information about your process, you don't actually need a profiler on Linux.
You can use
topin batch mode. It runs in the batch mode either until it is killed or until N iterations is done:top -b -p `pidof a.out`or
top -b -p `pidof a.out` -n 100and you will get this:
$ top -b -p `pidof a.out` top - 10:31:50 up 12 days, 19:08, 5 users, load average: 0.02, 0.01, 0.02 Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie Cpu(s): 0.0%us, 0.0%sy, 0.0%ni,100.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 16330584k total, 2335024k used, 13995560k free, 241348k buffers Swap: 4194296k total, 0k used, 4194296k free, 1631880k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24402 SK 20 0 98.7m 1056 860 S 43.9 0.0 0:11.87 a.out top - 10:31:53 up 12 days, 19:08, 5 users, load average: 0.02, 0.01, 0.02 Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie Cpu(s): 0.9%us, 3.7%sy, 0.0%ni, 95.5%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 16330584k total, 2335148k used, 13995436k free, 241348k buffers Swap: 4194296k total, 0k used, 4194296k free, 1631880k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 24402 SK 20 0 98.7m 1072 860 S 19.0 0.0 0:12.44 a.outYou can use
ps(for instance in a shell script)ps --format pid,pcpu,cputime,etime,size,vsz,cmd -p `pidof a.out`I need some means of recording the performance of an application on a Linux machine
In order to do this you need to use
perfif your Linux kernel is greater than 2.6.32 or OProfile if it is older. Both programs don't require from you to instrument your program (like Gprof requires). However, in order to get the call graph correctly inperfyou need to build you program with -fno-omit-frame-pointer. For example:g++ -fno-omit-frame-pointer -O2 main.cpp.
As for Linux perf:
To record performance data:
perf record -p `pidof a.out`or to record for 10 seconds:
perf record -p `pidof a.out` sleep 10or to record with a call graph ()
perf record -g -p `pidof a.out`To analyze the recorded data
perf report --stdio perf report --stdio --sort=dso -g none perf report --stdio -g none perf report --stdio -gOn RHEL 6.3 it is allowed to read /boot/System.map-2.6.32-279.el6.x86_64, so I usually add --kallsyms=/boot/System.map-2.6.32-279.el6.x86_64 when doing a performance report:
perf report --stdio -g --kallsyms=/boot/System.map-2.6.32-279.el6.x86_64
Here I wrote some more information on using Linux `perf`:First of all - this is tutorial about Linux profiling with perf
You can use perf if your Linux Kernel is greater than 2.6.32 or OProfile if it is older. Both programs don't require from you to instrument your program (like Gprof requires). However, in order to get call graph correctly in perf you need to build you program with
-fno-omit-frame-pointer. For example:g++ -fno-omit-frame-pointer -O2 main.cpp.You can see a "live" analysis of your application with perf top:
sudo perf top -p `pidof a.out` -K
Or you can record performance data of a running application and analyze them after that:
To record performance data:
perf record -p `pidof a.out`or to record for 10 seconds:
perf record -p `pidof a.out` sleep 10or to record with a call graph ()
perf record -g -p `pidof a.out`To analyze the recorded data
perf report --stdio
perf report --stdio --sort=dso -g none
perf report --stdio -g none
perf report --stdio -g
Or you can record performance data of an application and analyze them after that just by launching the application in this way and waiting for it to exit:
perf record ./a.out
This is an example of profiling a test program.
The test program is in file main.cpp (main.cpp is at the bottom of the answer):
I compile it in this way:
g++ -m64 -fno-omit-frame-pointer -g main.cpp -L. -ltcmalloc_minimal -o my_test
I use libmalloc_minimial.so since it is compiled with -fno-omit-frame-pointer while libc malloc seems to be compiled without this option. Then I run my test program:
./my_test 100000000
Then I record performance data of a running process:
perf record -g -p `pidof my_test` -o ./my_test.perf.data sleep 30
Then I analyze the load per module:
perf report --stdio -g none --sort comm,dso -i ./my_test.perf.data
# Overhead Command Shared Object
# ........ ....... ............................
#
70.06% my_test my_test
28.33% my_test libtcmalloc_minimal.so.0.1.0
1.61% my_test [kernel.kallsyms]
Then load per function is analyzed:
perf report --stdio -g none -i ./my_test.perf.data | c++filt
# Overhead Command Shared Object Symbol
# ........ ....... ............................ ...........................
#
29.30% my_test my_test [.] f2(long)
29.14% my_test my_test [.] f1(long)
15.17% my_test libtcmalloc_minimal.so.0.1.0 [.] operator new(unsigned long)
13.16% my_test libtcmalloc_minimal.so.0.1.0 [.] operator delete(void*)
9.44% my_test my_test [.] process_request(long)
1.01% my_test my_test [.] operator delete(void*)@plt
0.97% my_test my_test [.] operator new(unsigned long)@plt
0.20% my_test my_test [.] main
0.19% my_test [kernel.kallsyms] [k] apic_timer_interrupt
0.16% my_test [kernel.kallsyms] [k] _spin_lock
0.13% my_test [kernel.kallsyms] [k] native_write_msr_safe
and so on ...
Then call chains are analyzed:
perf report --stdio -g graph -i ./my_test.perf.data | c++filt
# Overhead Command Shared Object Symbol
# ........ ....... ............................ ...........................
#
29.30% my_test my_test [.] f2(long)
|
--- f2(long)
|
--29.01%-- process_request(long)
main
__libc_start_main
29.14% my_test my_test [.] f1(long)
|
--- f1(long)
|
|--15.05%-- process_request(long)
| main
| __libc_start_main
|
--13.79%-- f2(long)
process_request(long)
main
__libc_start_main
15.17% my_test libtcmalloc_minimal.so.0.1.0 [.] operator new(unsigned long)
|
--- operator new(unsigned long)
|
|--11.44%-- f1(long)
| |
| |--5.75%-- process_request(long)
| | main
| | __libc_start_main
| |
| --5.69%-- f2(long)
| process_request(long)
| main
| __libc_start_main
|
--3.01%-- process_request(long)
main
__libc_start_main
13.16% my_test libtcmalloc_minimal.so.0.1.0 [.] operator delete(void*)
|
--- operator delete(void*)
|
|--9.13%-- f1(long)
| |
| |--4.63%-- f2(long)
| | process_request(long)
| | main
| | __libc_start_main
| |
| --4.51%-- process_request(long)
| main
| __libc_start_main
|
|--3.05%-- process_request(long)
| main
| __libc_start_main
|
--0.80%-- f2(long)
process_request(long)
main
__libc_start_main
9.44% my_test my_test [.] process_request(long)
|
--- process_request(long)
|
--9.39%-- main
__libc_start_main
1.01% my_test my_test [.] operator delete(void*)@plt
|
--- operator delete(void*)@plt
0.97% my_test my_test [.] operator new(unsigned long)@plt
|
--- operator new(unsigned long)@plt
0.20% my_test my_test [.] main
0.19% my_test [kernel.kallsyms] [k] apic_timer_interrupt
0.16% my_test [kernel.kallsyms] [k] _spin_lock
and so on ...
So at this point you know where your program spends time.
And this is the main.cpp file for the test:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
time_t f1(time_t time_value)
{
for (int j = 0; j < 10; ++j) {
++time_value;
if (j%5 == 0) {
double *p = new double;
delete p;
}
}
return time_value;
}
time_t f2(time_t time_value)
{
for (int j = 0; j < 40; ++j) {
++time_value;
}
time_value = f1(time_value);
return time_value;
}
time_t process_request(time_t time_value)
{
for (int j = 0; j < 10; ++j) {
int *p = new int;
delete p;
for (int m = 0; m < 10; ++m) {
++time_value;
}
}
for (int i = 0; i < 10; ++i) {
time_value = f1(time_value);
time_value = f2(time_value);
}
return time_value;
}
int main(int argc, char* argv2[])
{
int number_loops = argc > 1 ? atoi(argv2[1]) : 1;
time_t time_value = time(0);
printf("number loops %d\n", number_loops);
printf("time_value: %d\n", time_value);
for (int i = 0; i < number_loops; ++i) {
time_value = process_request(time_value);
}
printf("time_value: %ld\n", time_value);
return 0;
}
Quoting Linus Torvalds himself:
Don't use gprof. You're much better off using the newish Linux 'perf' tool.
And later ...
I can pretty much guarantee that once you start using it, you'll never use gprof or oprofile again.
See Re: [PATCH] grep: do not do external grep on skip-worktree entries (2010-01-04)