Kernel perf tool user guide

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Derick McDonald
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1 Kernel perf tool user guide

2 Reversion Record Date Rev Change Description Author V0.1 Inital Zhang Yongchang 1 / 10

3 catalog 1 PURPOSE TERMINOLOGY ENVIRONMENT HARDWARE PLATFORM SOFTWARE PLATFORM INSTALL GUIDE DOWNLOAD THE LINUX KERNEL ENVIRONMENT PREPARED COMPILE USE GUIDE PERF LIST PERF STAT PERF TOP PERF RECORD AND PERF REPORT OTHER PERF COMMAND DESCRIPTION / 10

4 Figure index Figure 1 perf list output...6 Figure 2 perf stat output...7 Figure 3 perf top output...8 Figure 4 perf report output / 10

5 1 Purpose This guide help user to install the perf on ARM. And introduce the base command. 2 Terminology perf: perf (sometimes called perf_events or perf tools, originally Performance Counters for Linux, PCL) is a performance analyzing tool in Linux, available from Linux kernel version Userspace controlling utility, named perf, is accessed from the command line and provides a number of subcommands; it is capable of statistical profiling of the entire system (both kernel and userland code). Events: The perf tool supports a list of measurable events. The tool and underlying kernel interface can measure events coming from different sources. For instance, some event are pure kernel counters, in this case they are called software events. Examples include: context-switches, minor-faults. Another source of events is the processor itself and its Performance Monitoring Unit (PMU). It provides a list of events to measure micro-architectural events such as the number of cycles, instructions retired, L1 cache misses and so on. Those events are called PMU hardware events or hardware events for short. They vary with each processor type and model. The perf_events interface also provides a small set of common hardware events monikers. On each processor, those events get mapped onto an actual event provided by the CPU, if they exists, otherwise the event cannot be used. Somewhat confusingly, these are also called hardware events and hardware cache events. Finally, there are also tracepoint events which are implemented by the kernel ftrace infrastructure. Those are only available with the 2.6.3x and newer kernels. 3 Environment 3.1 Hardware Platform SOC: Rockchip RK3399 GPU: Mali T864 (800MHz) CPU: Dual-core Cortex-A72 up to 2.0GHz (real frequency is 1.8GHz) Quad-core Cortex-A53 up to 1.5GHz (real frequency is 1.4GHz) 3.2 Software Platform OS: Ubuntu (32bit) 4 / 10

6 4 Install Guide 4.1 Download the Linux kernel The perf is a part of the kernel, so download the kernel code. wget mv release release tar.gz tar xvf release tar.gz To assume the code directory kernel source code:~/kernel-release Environment Prepared sudo apt-get install flex bison libelf-dev libaudit-dev libdw-dev sudo apt-get install libunwind-dev python-dev sudo apt-get install binutils-dev libbfd-dev libelf1 libperl-dev sudo apt-get install libnuma-dev libunwind8 libunwind8-dev sudo apt-get install libslang2 libslang2-dev sudo apt-get install binutils-multiarch-dev elfutils libiberty-dev sudo apt-get install gcc-arm-linux-gnueabihf 4.3 Compile cd ~/kernel-release /tools/perf export ARCH="arm" export ARCHV="aarch32" make sudo make install prefix=/usr/ install If your system is 64bit, you should specific ARCH=arm64, ARCHV=aarch64. 5 / 10

7 5 Use Guide 5.1 Perf list Show supported events Figure 1 perf list output 5.2 Perf stat Create test1.c : #include <stdio.h> 6 / 10

void longfor() { int i = 0, j = 0; for(i = 0 ; i < 1000000 ; i++) j = i; } void foo1() { int i = 0; for(i = 0; i < 100 ; i++) longfor(); } int main(void) { foo1(); return 0; }

8 void longfor() { int i = 0, j = 0; for(i = 0 ; i < ; i++) j = i; } void foo1() { int i = 0; for(i = 0; i < 100 ; i++) longfor(); } int main(void) { foo1(); return 0; } Compile: gcc o test1 test1.c Run tes1 with the perf stat: Figure 2 perf stat output Task-clock(msec): CPUs utilization. The value is high, note that most of the time spend on the CPU. 7 / 10

9 Context-switches: The number of process switching. Recorded the process switching times, frequently process switching should be avoided. CPU-migrations: CPU migration times Cycles: count how many cycles spend Instructions: Machine Instructions count Branch-misses: Branch prediction miss count The test1 is a CPU bound program because the task-clock is 0.994, and it spend the most time on the function longfor(). For the complex program optimized jobs, using the perf is a good way. 5.3 Perf Top Create a test file test2.c: #include <stdio.h> int main(void) { int i = 0; while(1) i = 1; return 0; } Compile test2 and run test2: gcc o test2 test2.c./test2 Run perf top: Figure 3 perf top output 8 / 10

From the output, we can know: The first column: the proportion of the performance events caused by the symbol, the default refers to the proportion of CPU cycles occupied.

10 From the output, we can know: The first column: the proportion of the performance events caused by the symbol, the default refers to the proportion of CPU cycles occupied. The second column: DSO (Dynamic Shared Object), may be an application, kernel, dynamic link library and module. The third column: the type of DSO. [.] Indicates that this symbol belongs to the user's ELF file, including the executable file and the dynamic link library. [k] Indicates that this symbol belongs to a kernel or module. The fourth column: symbolic name. Some symbols can t be parsed as function names so just output the addresses. The CPU almost be taken up by the process main function. By this method, we can find who is busying now. 5.4 Perf Record and Perf Report Run test1 with perf record: perf record e cpu-clock./test1 Read the report with perf report: Figure 4 perf report output The first column 'Overhead': indicates the percentage of the overall samples collected in the corresponding function. 9 / 10

11 The second column: reports the process from which the samples were collected. In perthread/per-process mode, this is always the name of the monitored command. But in cpu-wide mode, the command can vary. The third column: shows the name of the ELF image where the samples came from. If a program is dynamically linked, then this may show the name of a shared library. When the samples come from the kernel, then the pseudo ELF image name [kernel.kallsyms] is used. The fourth column indicates the privilege level at which the sample was taken, i.e. when the program was running when it was interrupted: [.]: user level [k]: kernel level [g]: guest kernel level (virtualization) [u]: guest OS user space [H]: hypervisor The final column: shows the symbol name. 5.5 Other Perf command description Please read the perf wiki: 10 / 10

Linux Strace tool user guide

Linux Strace tool user guide 2017-10-13 Reversion Record Date Rev Change Description Author 2017-10-13 V0.1 Initial Zhang Yongchang 1 / 9 catalog 1 PURPOSE...4 2 TERMINOLOGY...4 3 ENVIRONMENT...4 3.1 HARDWARE