Performance Counters for Linux (PCL) is a new kernel-based subsystem that provides a framework for collecting and analyzing performance data. These events will vary based on the performance monitoring hardware and the software configuration of the system. Linux includes this kernel subsystem to collect data and the user-space tool perf to analyze the collected performance data.
Profiling is achieved by instrumenting either the program source code or its binary executable form using a tool called a profiler (or code profiler).
Linux hardware performance measurement using counters, trace-points, software performance counters, and dynamic probes. Perf as one of the two most commonly used performance counter profiling tools on Linux. Perf basically use to analyses the core internal bottleneck right up to the driver level.
Linux support many profiling tools like perf, trace-cmd, blktrace, strace and oprofile.
Below steps were tested on the XU3/XU4 platforms.
In order to build perf you need to install following pakages.
sudo apt-get install flex bison libdw-dev libnewt-dev binutils-dev libaudit-dev libgtk2.0-dev libperl-dev libpython-dev libunwind-*
Ensure the following kernel config options are enabled
$ zegrep "CONFIG_PERF_EVENTS|CONFIG_HW_PERF_EVENTS" /proc/config.gz CONFIG_PERF_EVENTS=y CONFIG_HW_PERF_EVENTS=y
| CONFIG_PERF_EVENTS | support for various performance events provided by software and hardware. |
| CONFIG_HW_PERF_EVENTS | support enables hardware performance counter support for perf events. |
| CONFIG_CGROUP_PERF | perf_event per-cpu per-container group (cgroup) monitoring. |
| CONFIG_PERF_USE_VMALLOC | some architectures that have d-cache aliasing issues, such as Sparc and ARM, should select PERF_USE_VMALLOC in order to avoid these for perf mmap. |
| CONFIG_FRAME_POINTER | kernel image will be slightly larger and slower, but it will give very useful debugging information |
| CONFIG_KALLSYMS | kernel print out symbolic crash information and symbolic stack backtraces. |
| CONFIG_TRACEPOINTS | Kernel event like usb, wireless event, malie event can handled using tracepoint. |
| CONFIG_FTRACE | Kernel ftrace is an internal tracer designed to help out developers and designers of systems to find what is going on inside the kernel. |
| CONFIG_KPROBES | Events are similar to tracepoint based events |
| CONFIG_KPROBE_EVENTS | |
| CONFIG_UPROBES | Uprobe based trace events are similar to kprobe based trace events. |
| CONFIG_UPROBE_EVENTS | |
| CONFIG_LOCK_STAT | Kernel lock stats is required. |
| CONFIG_DEBUG_INFO | Kernel enable debug info. |
Enable PMU setting in Device tree Perf events can be enable in the exynos5422_evt0.dtsi.
root@odroidcu4n:/usr/src/odroidxu3-3kr# git diff arch/arm/boot/dts/exynos5422_evt0.dtsi
diff --git a/arch/arm/boot/dts/exynos5422_evt0.dtsi b/arch/arm/boot/dts/exynos5422_evt0.dtsi
index 2f9c95d..74c7c7e 100755
--- a/arch/arm/boot/dts/exynos5422_evt0.dtsi
+++ b/arch/arm/boot/dts/exynos5422_evt0.dtsi
@@ -91,6 +91,17 @@
};
};
+ arm-pmu {
+ /* compatible = "arm,cortex-a15-pmu";
+ interrupt-parent = <&combiner>;
+ interrupts = <1 2>, <7 0>, <16 6>, <19 2>;
+ */
+ ompatible = "arm,cortex-a7-pmu";
+ interrupt-parent = <&gic>;
+ interrupts = <0 192 4>, <0 193 4>, <0 194 4>, <0 195 4>;
+ };
+
watchdog@10020000 {
compatible = "samsung,s3c2410-wdt";
reg = <0x101D0000 0x100>;
Note: Perf counters for arm,cotrex-a7-pmu is supported in the kernel. But not for arm,cortex-a15-pmu.
Once kernel is build using above config flags. Perf could be install using following command. If the distribution supports it.
sudo apt-get install linux-tools
Otherwise you need to build the took from the kernel source code tree.
# getting the source
$ git clone --depth 1 https://github.com/hardkernel/linux.git -b odroidxu3-3.10.y $ cd linux/tools/perf $ make -j `getconf _NPROCESSORS_ONLN` perf
# Install perf tool.
$ cp perf /usr/bin/
# test perf is installed and running.
$ perf list List of pre-defined events (to be used in -e): cpu-cycles OR cycles [Hardware event] instructions [Hardware event] cache-references [Hardware event] cache-misses [Hardware event] branch-instructions OR branches [Hardware event] branch-misses [Hardware event] bus-cycles [Hardware event] stalled-cycles-frontend OR idle-cycles-frontend [Hardware event] stalled-cycles-backend OR idle-cycles-backend [Hardware event] ref-cycles [Hardware event] cpu-clock [Software event] task-clock [Software event] page-faults OR faults [Software event] context-switches OR cs [Software event] cpu-migrations OR migrations [Software event] minor-faults [Software event] major-faults [Software event] . . .
perf tool measures the performance of the application and trace down to the kernel event that got triggers.
perf help
root@odroidcu4n:~# perf --help usage: perf [--version] [--help] COMMAND [ARGS] The most commonly used perf commands are: annotate Read perf.data (created by perf record) and display annotated code archive Create archive with object files with build-ids found in perf .data file bench General framework for benchmark suites buildid-cache Manage build-id cache. buildid-list List the buildids in a perf.data file diff Read two perf.data files and display the differential profile evlist List the event names in a perf.data file inject Filter to augment the events stream with additional informati on kmem Tool to trace/measure kernel memory(slab) properties kvm Tool to trace/measure kvm guest os list List all symbolic event types lock Analyze lock events mem Profile memory accesses record Run a command and record its profile into perf.data report Read perf.data (created by perf record) and display the profi le sched Tool to trace/measure scheduler properties (latencies) script Read perf.data (created by perf record) and display trace out put stat Run a command and gather performance counter statistics test Runs sanity tests. timechart Tool to visualize total system behavior during a workload top System profiling tool. trace strace inspired tool probe Define new dynamic tracepoints See 'perf help COMMAND' for more information on a specific command.
perf is used with several sub commands:
stat: This perf command provides overall statistics for common performance events,
including instructions executed and clock cycles consumed.
Options allow selection of events other than the default measurement events.
top: This perf command help monitor top-like dynamic view of hottest functions.
record: This perf command records performance data into a file which can be later analyzed using perf report.
report: This perf command reads the performance data from a file and analyzes the recorded data.
list: This perf command lists the events available on a particular machine.
Perf stats:
~# perf stat -B dd if=/dev/zero of=/dev/null count=1000000
1000000+0 records in
1000000+0 records out
512000000 bytes (512 MB) copied, 1.41271 s, 362 MB/s
Performance counter stats for 'dd if=/dev/zero of=/dev/null count=1000000':
1414.727540 task-clock # 0.998 CPUs utilized
10 context-switches # 0.007 K/sec
0 cpu-migrations # 0.000 K/sec
148 page-faults # 0.105 K/sec
<not supported> cycles
<not supported> stalled-cycles-frontend
<not supported> stalled-cycles-backend
<not supported> instructions
<not supported> branches
<not supported> branch-misses
1.416998532 seconds time elapsed
Node: perf stats provide summary of the kernel events.
Perf top:
Suppose we want to run-time analyses of the kernel events just like user space top/htop use below command.
perf top -z
~# perf top -z Samples: 127K of event 'cpu-clock', Event count (approx.): 3315322731 98.92% [kernel].head.text [k] 0xc0023f10 0.08% perf [.] sort__dso_cmp 0.07% perf [.] perf_top__mmap_read_idx 0.06% perf [.] perf_evsel__parse_sample 0.06% libc-2.21.so [.] memset 0.06% perf [.] perf_evlist__mmap_read 0.05% perf [.] add_hist_entry.isra.8 0.05% libpthread-2.21.so [.] pthread_mutex_lock 0.05% libslang.so.2.3.0 [.] 0x000630ce 0.04% perf [.] perf_event__preprocess_sample 0.03% libpthread-2.21.so [.] __pthread_mutex_unlock_usercnt 0.03% libslang.so.2.3.0 [.] SLsmg_write_chars 0.03% perf [.] symbols__insert 0.03% libc-2.21.so [.] __libc_calloc 0.03% perf [.] maps__find 0.03% libc-2.21.so [.] strstr 0.02% libc-2.21.so [.] strcmp 0.02% perf [.] dump_printf 0.02% perf [.] dso__find_symbol 0.01% perf [.] symbol_filter
Note: You can watch all the supported list events on the perf top.
perf top -z -e task-clock
~# perf top -z -e task-clock Samples: 1M of event 'task-clock', Event count (approx.): 2069462202 99.22% [kernel].head.text [k] 0xc0023f10 0.06% perf [.] sort__dso_cmp 0.06% libc-2.21.so [.] memset 0.06% perf [.] add_hist_entry.isra.8 0.06% perf [.] perf_evlist__mmap_read 0.06% perf [.] perf_top__mmap_read_idx 0.05% perf [.] perf_evsel__parse_sample 0.04% perf [.] perf_event__preprocess_sample 0.04% libpthread-2.21.so [.] pthread_mutex_lock 0.03% libslang.so.2.3.0 [.] SLsmg_write_chars 0.03% libpthread-2.21.so [.] __pthread_mutex_unlock_usercnt 0.03% perf [.] maps__find 0.03% libslang.so.2.3.0 [.] 0x000548d2 0.03% perf [.] dump_printf 0.03% libc-2.21.so [.] strcmp
Perf record
perf record is use to record the kernel event into perf.data, that file can then be analyzed, possibly on another machine, using the perf report and perf annotate commands.
~# perf record dd if=/dev/zero of=/dev/null count=1000000 1000000+0 records in 1000000+0 records out 512000000 bytes (512 MB) copied, 1.50392 s, 340 MB/s [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.232 MB perf.data (~10121 samples) ] ~# ~# ls perf.data perf.data
Perf report
Samples collected by perf record are saved into a binary file called, by default, perf.data. The perf report command reads this file and generates a concise execution profile.
Samples: 6K of event 'cpu-clock', Event count (approx.): 1503750000 13.68% dd [kernel.kallsyms] [k] vector_swi 10.97% dd [kernel.kallsyms] [k] lock_acquire 9.64% dd dd [.] 0x000020fc 7.45% dd [kernel.kallsyms] [k] __srcu_read_lock 7.27% dd [kernel.kallsyms] [k] __srcu_read_unlock 6.42% dd [kernel.kallsyms] [k] __clear_user_std 6.12% dd [kernel.kallsyms] [k] lock_release 4.66% dd libc-2.21.so [.] __GI___libc_read 4.59% dd libc-2.21.so [.] __GI___libc_write 4.24% dd [kernel.kallsyms] [k] fsnotify 3.14% dd [kernel.kallsyms] [k] vfs_write 2.81% dd [kernel.kallsyms] [k] vfs_read 2.79% dd libc-2.21.so [.] __GI___memcpy_neon 2.76% dd [kernel.kallsyms] [k] fget_light 1.78% dd [kernel.kallsyms] [k] SyS_write 1.75% dd [kernel.kallsyms] [k] SyS_read 1.68% dd [kernel.kallsyms] [k] rw_verify_area 1.60% dd [kernel.kallsyms] [k] ret_fast_syscall 1.36% dd [kernel.kallsyms] [k] read_zero 1.10% dd [kernel.kallsyms] [k] local_restart 1.08% dd [kernel.kallsyms] [k] __fsnotify_parent 0.90% dd [kernel.kallsyms] [k] debug_smp_processor_id
You can find more on following links.
https://perf.wiki.kernel.org/index.php/Tutorial