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                <ol class="chapter"><li class="chapter-item expanded affix "><a href="../intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="../shells/index.html"><strong aria-hidden="true">1.</strong> Shells</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../shells/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="../shells/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="../shells/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li></ol></li><li class="chapter-item expanded "><a href="../cli/index.html"><strong aria-hidden="true">2.</strong> CLI foo</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../cli/awk.html"><strong aria-hidden="true">2.1.</strong> awk</a></li><li class="chapter-item expanded "><a href="../cli/sed.html"><strong aria-hidden="true">2.2.</strong> sed</a></li><li class="chapter-item expanded "><a href="../cli/column.html"><strong aria-hidden="true">2.3.</strong> column</a></li><li class="chapter-item expanded "><a href="../cli/sort.html"><strong aria-hidden="true">2.4.</strong> sort</a></li><li class="chapter-item expanded "><a href="../cli/tr.html"><strong aria-hidden="true">2.5.</strong> tr</a></li></ol></li><li class="chapter-item expanded "><a href="../tools/index.html"><strong aria-hidden="true">3.</strong> Tools</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../tools/tmux.html"><strong aria-hidden="true">3.1.</strong> tmux</a></li><li class="chapter-item expanded "><a href="../tools/emacs.html"><strong aria-hidden="true">3.2.</strong> emacs</a></li><li class="chapter-item expanded "><a href="../tools/gpg.html"><strong aria-hidden="true">3.3.</strong> gpg</a></li><li class="chapter-item expanded "><a href="../tools/radare2.html"><strong aria-hidden="true">3.4.</strong> radare2</a></li><li class="chapter-item expanded "><a href="../tools/qemu.html"><strong aria-hidden="true">3.5.</strong> qemu</a></li><li class="chapter-item expanded "><a href="../tools/pacman.html"><strong aria-hidden="true">3.6.</strong> pacman</a></li><li class="chapter-item expanded "><a href="../tools/dot.html"><strong aria-hidden="true">3.7.</strong> dot</a></li><li class="chapter-item expanded "><a href="../tools/ffmpeg.html"><strong aria-hidden="true">3.8.</strong> ffmpeg</a></li><li class="chapter-item expanded "><a href="../tools/gnuplot.html"><strong aria-hidden="true">3.9.</strong> gnuplot</a></li><li class="chapter-item expanded "><a href="../tools/restic.html"><strong aria-hidden="true">3.10.</strong> restic</a></li><li class="chapter-item expanded "><a href="../tools/qrencode.html"><strong aria-hidden="true">3.11.</strong> qrencode</a></li></ol></li><li class="chapter-item expanded "><a href="../monitor/index.html"><strong aria-hidden="true">4.</strong> Resource analysis & monitor</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../monitor/lsof.html"><strong aria-hidden="true">4.1.</strong> lsof</a></li><li class="chapter-item expanded "><a href="../monitor/pidstat.html"><strong aria-hidden="true">4.2.</strong> pidstat</a></li><li class="chapter-item expanded "><a href="../monitor/pgrep.html"><strong aria-hidden="true">4.3.</strong> pgrep</a></li><li class="chapter-item expanded "><a href="../monitor/ps.html"><strong aria-hidden="true">4.4.</strong> ps</a></li><li class="chapter-item expanded "><a href="../monitor/pmap.html"><strong aria-hidden="true">4.5.</strong> pmap</a></li><li class="chapter-item expanded "><a href="../monitor/pstack.html"><strong aria-hidden="true">4.6.</strong> pstack</a></li></ol></li><li class="chapter-item expanded "><a href="../trace_profile/index.html"><strong aria-hidden="true">5.</strong> Trace and Profile</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../trace_profile/time.html"><strong aria-hidden="true">5.1.</strong> time</a></li><li class="chapter-item expanded "><a href="../trace_profile/strace.html"><strong aria-hidden="true">5.2.</strong> strace</a></li><li class="chapter-item expanded "><a href="../trace_profile/ltrace.html"><strong aria-hidden="true">5.3.</strong> ltrace</a></li><li class="chapter-item expanded "><a href="../trace_profile/perf.html" class="active"><strong aria-hidden="true">5.4.</strong> perf</a></li><li class="chapter-item expanded "><a href="../trace_profile/oprofile.html"><strong aria-hidden="true">5.5.</strong> OProfile</a></li><li class="chapter-item expanded "><a href="../trace_profile/callgrind.html"><strong aria-hidden="true">5.6.</strong> callgrind</a></li></ol></li><li class="chapter-item expanded "><a href="../debug/index.html"><strong aria-hidden="true">6.</strong> Debug</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../debug/gdb.html"><strong aria-hidden="true">6.1.</strong> gdb</a></li><li class="chapter-item expanded "><a href="../debug/gdbserver.html"><strong aria-hidden="true">6.2.</strong> gdbserver</a></li></ol></li><li class="chapter-item expanded "><a href="../binary/index.html"><strong aria-hidden="true">7.</strong> Binary</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../binary/od.html"><strong aria-hidden="true">7.1.</strong> od</a></li><li class="chapter-item expanded "><a href="../binary/xxd.html"><strong aria-hidden="true">7.2.</strong> xxd</a></li><li class="chapter-item expanded "><a href="../binary/readelf.html"><strong aria-hidden="true">7.3.</strong> readelf</a></li><li class="chapter-item expanded "><a href="../binary/objdump.html"><strong aria-hidden="true">7.4.</strong> objdump</a></li><li class="chapter-item expanded "><a href="../binary/nm.html"><strong aria-hidden="true">7.5.</strong> nm</a></li></ol></li><li class="chapter-item expanded "><a href="../development/index.html"><strong aria-hidden="true">8.</strong> Development</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../development/c++filt.html"><strong aria-hidden="true">8.1.</strong> c++filt</a></li><li class="chapter-item expanded "><a href="../development/c++.html"><strong aria-hidden="true">8.2.</strong> c++</a></li><li class="chapter-item expanded "><a href="../development/glibc.html"><strong aria-hidden="true">8.3.</strong> glibc</a></li><li class="chapter-item expanded "><a href="../development/gcc.html"><strong aria-hidden="true">8.4.</strong> gcc</a></li><li class="chapter-item expanded "><a href="../development/git.html"><strong aria-hidden="true">8.5.</strong> git</a></li><li class="chapter-item expanded "><a href="../development/cmake.html"><strong aria-hidden="true">8.6.</strong> cmake</a></li><li class="chapter-item expanded "><a href="../development/make.html"><strong aria-hidden="true">8.7.</strong> make</a></li><li class="chapter-item expanded "><a href="../development/ld.so.html"><strong aria-hidden="true">8.8.</strong> ld.so</a></li><li class="chapter-item expanded "><a href="../development/symbolver.html"><strong aria-hidden="true">8.9.</strong> symbol versioning</a></li><li class="chapter-item expanded "><a href="../development/python.html"><strong aria-hidden="true">8.10.</strong> python</a></li><li class="chapter-item expanded "><a href="../development/gcov.html"><strong aria-hidden="true">8.11.</strong> gcov</a></li><li class="chapter-item expanded "><a href="../development/pgo.html"><strong aria-hidden="true">8.12.</strong> pgo</a></li></ol></li><li class="chapter-item expanded "><a href="../linux/index.html"><strong aria-hidden="true">9.</strong> Linux</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../linux/systemd.html"><strong aria-hidden="true">9.1.</strong> systemd</a></li><li class="chapter-item expanded "><a href="../linux/coredump.html"><strong aria-hidden="true">9.2.</strong> coredump</a></li><li class="chapter-item expanded "><a href="../linux/ptrace_scope.html"><strong aria-hidden="true">9.3.</strong> ptrace_scope</a></li><li class="chapter-item expanded "><a href="../linux/cryptsetup.html"><strong aria-hidden="true">9.4.</strong> cryptsetup</a></li><li class="chapter-item expanded "><a href="../linux/swap.html"><strong aria-hidden="true">9.5.</strong> swap</a></li><li class="chapter-item expanded "><a href="../linux/input.html"><strong aria-hidden="true">9.6.</strong> input</a></li><li class="chapter-item expanded "><a href="../linux/acl.html"><strong aria-hidden="true">9.7.</strong> acl</a></li><li class="chapter-item expanded "><a href="../linux/zfs.html"><strong aria-hidden="true">9.8.</strong> zfs</a></li></ol></li><li class="chapter-item expanded "><a href="../network/index.html"><strong aria-hidden="true">10.</strong> Network</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../network/ss.html"><strong aria-hidden="true">10.1.</strong> ss</a></li><li class="chapter-item expanded "><a href="../network/tcpdump.html"><strong aria-hidden="true">10.2.</strong> tcpdump</a></li><li class="chapter-item expanded "><a href="../network/tshark.html"><strong aria-hidden="true">10.3.</strong> tshark</a></li><li class="chapter-item expanded "><a href="../network/firewall-cmd.html"><strong aria-hidden="true">10.4.</strong> firewall-cmd</a></li><li class="chapter-item expanded "><a href="../network/nftables.html"><strong aria-hidden="true">10.5.</strong> nftables</a></li></ol></li><li class="chapter-item expanded "><a href="../web/index.html"><strong aria-hidden="true">11.</strong> Web</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../web/html.html"><strong aria-hidden="true">11.1.</strong> html</a></li><li class="chapter-item expanded "><a href="../web/css.html"><strong aria-hidden="true">11.2.</strong> css</a></li><li class="chapter-item expanded "><a href="../web/chartjs.html"><strong aria-hidden="true">11.3.</strong> chartjs</a></li></ol></li><li class="chapter-item expanded "><a href="../arch/index.html"><strong aria-hidden="true">12.</strong> Arch</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../arch/x86_64.html"><strong aria-hidden="true">12.1.</strong> x86_64</a></li><li class="chapter-item expanded "><a href="../arch/armv8.html"><strong aria-hidden="true">12.2.</strong> armv8</a></li><li class="chapter-item expanded "><a href="../arch/arm64.html"><strong aria-hidden="true">12.3.</strong> arm64</a></li><li class="chapter-item expanded "><a href="../arch/armv7.html"><strong aria-hidden="true">12.4.</strong> armv7</a></li><li class="chapter-item expanded "><a href="../arch/riscv.html"><strong aria-hidden="true">12.5.</strong> riscv</a></li></ol></li></ol>
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                        <h1 id="perf1"><a class="header" href="#perf1">perf(1)</a></h1>
<pre><code>perf list     show supported hw/sw events &amp; metrics
  -v ........ print longer event descriptions
  --details . print information on the perf event names
              and expressions used internally by events

perf stat
  -p &lt;pid&gt; ..... show stats for running process
  -o &lt;file&gt; .... write output to file (default stderr)
  -I &lt;ms&gt; ...... show stats periodically over interval &lt;ms&gt;
  -e &lt;ev&gt; ...... select event(s)
  -M &lt;met&gt; ..... print metric(s), this adds the metric events
  --all-user ... configure all selected events for user space
  --all-kernel . configure all selected events for kernel space

perf top
  -p &lt;pid&gt; .. show stats for running process
  -F &lt;hz&gt; ... sampling frequency
  -K ........ hide kernel threads

perf record
  -p &lt;pid&gt; ............... record stats for running process
  -o &lt;file&gt; .............. write output to file (default perf.data)
  -F &lt;hz&gt; ................ sampling frequency
  --call-graph &lt;method&gt; .. [fp, dwarf, lbr] method how to caputre backtrace
                           fp   : use frame-pointer, need to compile with
                                  -fno-omit-frame-pointer
                           dwarf: use .cfi debug information
                           lbr  : use hardware last branch record facility
  -g ..................... short-hand for --call-graph fp
  -e &lt;ev&gt; ................ select event(s)
  --all-user ............. configure all selected events for user space
  --all-kernel ........... configure all selected events for kernel space
  -M intel ............... use intel disassembly in annotate

perf report
  -n .................... annotate symbols with nr of samples
  --stdio ............... report to stdio, if not presen tui mode
  -g graph,0.5,callee ... show callee based call chains with value &gt;0.5
</code></pre>
<pre><code>Useful &lt;ev&gt;:
  page-faults
  minor-faults
  major-faults
  cpu-cycles`
  task-clock
</code></pre>
<h2 id="select-specific-events"><a class="header" href="#select-specific-events">Select specific events</a></h2>
<p>Events to sample are specified with the <code>-e</code> option, either pass a comma
separated list or pass <code>-e</code> multiple times.</p>
<p>Events are specified in the following form <code>name[:modifier]</code>. The list and
description of the <code>modifier</code> can be found in the
<a href="https://man7.org/linux/man-pages/man1/perf-list.1.html"><code>perf-list(1)</code></a> manpage under <code>EVENT MODIFIERS</code>.</p>
<pre><code class="language-sh"># L1 i$ misses in user space
# L2 i$ stats in user/kernel space mixed
# Sample specified events.
perf stat -e L1-icache-load-misses:u \
          -e l2_rqsts.all_code_rd:uk,l2_rqsts.code_rd_hit:k,l2_rqsts.code_rd_miss:k \
          -- stress -c 2
</code></pre>
<p>The <code>--all-user</code> and <code>--all-kernel</code> options append a <code>:u</code> and <code>:k</code> modifier to
all specified events. Therefore the following two command lines are equivalent.</p>
<pre><code class="language-sh"># 1)
perf stat -e cycles:u,instructions:u -- ls

# 2)
perf stat --all-user -e cycles,instructions -- ls
</code></pre>
<h3 id="raw-events"><a class="header" href="#raw-events">Raw events</a></h3>
<p>In case perf does not provide a <em>symbolic</em> name for an event, the event can be
specified in a <em>raw</em> form as <code>r + UMask + EventCode</code>.</p>
<p>The following is an example for the <a href="https://github.com/intel/perfmon/blob/09c155f72e1b8f14b09aea346a35467a03a7d62b/SNB/events/sandybridge_core.json#L808">L2_RQSTS.CODE_RD_HIT</a> event
with <code>EventCode=0x24</code> and <code>UMask=0x10</code> on my laptop with a <code>sandybridge</code> uarch.</p>
<pre><code class="language-sh">perf stat -e l2_rqsts.code_rd_hit -e r1024 -- ls
# Performance counter stats for 'ls':
#
#       33.942      l2_rqsts.code_rd_hit
#       33.942      r1024
</code></pre>
<h3 id="find-raw-performance-counter-events-intel"><a class="header" href="#find-raw-performance-counter-events-intel">Find raw performance counter events (intel)</a></h3>
<p>The <a href="https://github.com/intel/perfmon"><code>intel/perfmon</code></a> repository provides a performance event
databases for the different intel uarchs.</p>
<p>The table in <a href="https://github.com/intel/perfmon/blob/main/mapfile.csv"><code>mapfile.csv</code></a> can be used to lookup the
corresponding uarch, just grab the family model from the procfs.</p>
<pre><code class="language-sh"> cat /proc/cpuinfo | awk '/^vendor_id/  { V=$3 }
                          /^cpu family/ { F=$4 }
                          /^model\s*:/  { printf "%s-%d-%x\n",V,F,$3 }'
</code></pre>
<blockquote>
<p>The table in <a href="https://github.com/intel/perfmon/tree/main#performance-monitoring-events">performance monitoring events</a> describes how
events are sorted into the different files.</p>
</blockquote>
<h3 id="raw-events-for-perfs-own-symbolic-names"><a class="header" href="#raw-events-for-perfs-own-symbolic-names">Raw events for perfs own symbolic names</a></h3>
<p>Perf also defines some own <em>symbolic</em> names for events. An example is the
<code>cache-references</code> event. The <a href="https://man7.org/linux/man-pages/man2/perf_event_open.2.html"><code>perf_event_open(2)</code></a> manpage
gives the following description.</p>
<pre><code class="language-man">perf_event_open(2)

PERF_COUNT_HW_CACHE_REFERENCES
    Cache accesses.  Usually this indicates Last Level Cache accesses but this
    may vary depending on your CPU.  This may include prefetches and coherency
    messages; again this depends on the design of your CPU.
</code></pre>
<p>The <code>sysfs</code> can be consulted to get the concrete performance counter on the
given system.</p>
<pre><code class="language-sh">cat /sys/devices/cpu/events/cache-misses
# event=0x2e,umask=0x41
</code></pre>
<h2 id="flamegraph"><a class="header" href="#flamegraph"><a href="https://github.com/brendangregg/FlameGraph"><code>Flamegraph</code></a></a></h2>
<h3 id="flamegraph-with-single-event-trace"><a class="header" href="#flamegraph-with-single-event-trace">Flamegraph with single event trace</a></h3>
<pre><code>perf record -g -e cpu-cycles -p &lt;pid&gt;
perf script | FlameGraph/stackcollapse-perf.pl | FlameGraph/flamegraph.pl &gt; cycles-flamegraph.svg
</code></pre>
<h3 id="flamegraph-with-multiple-event-traces"><a class="header" href="#flamegraph-with-multiple-event-traces">Flamegraph with multiple event traces</a></h3>
<pre><code class="language-sh">perf record -g -e cpu-cycles,page-faults -p &lt;pid&gt;
perf script --per-event-dump
# fold &amp; generate as above
</code></pre>
<h2 id="examples"><a class="header" href="#examples">Examples</a></h2>
<h3 id="estimate-max-instructions-per-cycle"><a class="header" href="#estimate-max-instructions-per-cycle">Estimate max instructions per cycle</a></h3>
<pre><code class="language-c">#define NOP4        "nop\nnop\nnop\nnop\n"
#define NOP32       NOP4   NOP4   NOP4   NOP4   NOP4   NOP4   NOP4   NOP4
#define NOP256      NOP32  NOP32  NOP32  NOP32  NOP32  NOP32  NOP32  NOP32
#define NOP2048     NOP256 NOP256 NOP256 NOP256 NOP256 NOP256 NOP256 NOP256

int main() {
  for (unsigned i = 0; i &lt; 2000000; ++i) {
    asm volatile(NOP2048);
  }
}
</code></pre>
<pre><code class="language-sh">perf stat -e cycles,instructions ./noploop
# Performance counter stats for './noploop':
#
#     1.031.075.940      cycles
#     4.103.534.341      instructions       #    3,98  insn per cycle
</code></pre>
<h3 id="caller-vs-callee-callstacks"><a class="header" href="#caller-vs-callee-callstacks">Caller vs callee callstacks</a></h3>
<p>The following gives an example for a scenario where we have the following calls</p>
<ul>
<li><code>main -&gt; do_foo() -&gt; do_work()</code></li>
<li><code>main -&gt; do_bar() -&gt; do_work()</code></li>
</ul>
<pre><code class="language-sh">perf report --stdio -g graph,callee

# Children      Self  Command  Shared Object         Symbols
# ........  ........  .......  ....................  .................
#
#  49.71%    49.66%   bench    bench                 [.] do_work
#          |
#           --49.66%--_start                &lt;- callstack bottom
#                     __libc_start_main
#                     0x7ff366c62ccf
#                     main
#                     |
#                     |--25.13%--do_bar
#                     |          do_work    &lt;- callstack top
#                     |
#                      --24.53%--do_foo
#                                do_work

perf report --stdio -g graph,callee

# Children      Self  Command  Shared Object         Symbols
# ........  ........  .......  ....................  .................
#
#  49.71%    49.66%   bench    bench                 [.] do_work
#          |
#          ---do_work                       &lt;- callstack top
#             |
#             |--25.15%--do_bar
#             |          main
#             |          0x7ff366c62ccf
#             |          __libc_start_main
#             |          _start             &lt;- callstack bottom
#             |
#              --24.55%--do_foo
#                        main
#                        0x7ff366c62ccf
#                        __libc_start_main
#                        _start             &lt;- callstack bottom
</code></pre>
<h2 id="references"><a class="header" href="#references">References</a></h2>
<ul>
<li><a href="https://github.com/intel/perfmon">intel/perfmon</a> - intel PMU event database per uarch</li>
<li><a href="https://perfmon-events.intel.com/">intel/perfmon-html</a> - a html rendered version of the PMU
events with search</li>
<li><a href="https://github.com/intel/perfmon/blob/main/mapfile.csv">intel/perfmon/mapfile.csv</a> - processor family to uarch mapping</li>
<li><a href="https://github.com/torvalds/linux/tree/master/tools/perf/pmu-events/arch/x86">linux/perf/events</a> - x86 PMU events known to perf tools</li>
<li><a href="https://github.com/torvalds/linux/blob/master/arch/x86/events/intel/core.c">linux/arch/events</a> - x86 PMU events linux kernel</li>
<li><a href="https://en.wikichip.org/wiki/WikiChip">wikichip</a> - computer architecture wiki</li>
<li><a href="https://man7.org/linux/man-pages/man1/perf-list.1.html">perf-list(1)</a> - manpage</li>
<li><a href="https://man7.org/linux/man-pages/man2/perf_event_open.2.html">perf_event_open(2)</a> - manpage</li>
<li><a href="https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html">intel/sdm</a> - intel software developer manuals (eg Optimization
Reference Manual)</li>
</ul>

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                <ol class="chapter"><li class="chapter-item expanded affix "><a href="../intro.html">Introduction</a></li><li class="chapter-item expanded "><a href="../shells/index.html"><strong aria-hidden="true">1.</strong> Shells</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../shells/zsh.html"><strong aria-hidden="true">1.1.</strong> zsh</a></li><li class="chapter-item expanded "><a href="../shells/bash.html"><strong aria-hidden="true">1.2.</strong> bash</a></li><li class="chapter-item expanded "><a href="../shells/fish.html"><strong aria-hidden="true">1.3.</strong> fish</a></li></ol></li><li class="chapter-item expanded "><a href="../cli/index.html"><strong aria-hidden="true">2.</strong> CLI foo</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../cli/awk.html"><strong aria-hidden="true">2.1.</strong> awk</a></li><li class="chapter-item expanded "><a href="../cli/sed.html"><strong aria-hidden="true">2.2.</strong> 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href="../trace_profile/time.html"><strong aria-hidden="true">5.1.</strong> time</a></li><li class="chapter-item expanded "><a href="../trace_profile/strace.html"><strong aria-hidden="true">5.2.</strong> strace</a></li><li class="chapter-item expanded "><a href="../trace_profile/ltrace.html"><strong aria-hidden="true">5.3.</strong> ltrace</a></li><li class="chapter-item expanded "><a href="../trace_profile/perf.html" class="active"><strong aria-hidden="true">5.4.</strong> perf</a></li><li class="chapter-item expanded "><a href="../trace_profile/oprofile.html"><strong aria-hidden="true">5.5.</strong> OProfile</a></li><li class="chapter-item expanded "><a href="../trace_profile/callgrind.html"><strong aria-hidden="true">5.6.</strong> callgrind</a></li></ol></li><li class="chapter-item expanded "><a href="../debug/index.html"><strong aria-hidden="true">6.</strong> Debug</a></li><li><ol class="section"><li class="chapter-item expanded "><a href="../debug/gdb.html"><strong 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                        <h1 id="perf1"><a class="header" href="#perf1">perf(1)</a></h1>
<pre><code>perf list     show supported hw/sw events &amp; metrics
  -v ........ print longer event descriptions
  --details . print information on the perf event names
              and expressions used internally by events

perf stat
  -p &lt;pid&gt; ..... show stats for running process
  -o &lt;file&gt; .... write output to file (default stderr)
  -I &lt;ms&gt; ...... show stats periodically over interval &lt;ms&gt;
  -e &lt;ev&gt; ...... select event(s)
  -M &lt;met&gt; ..... print metric(s), this adds the metric events
  --all-user ... configure all selected events for user space
  --all-kernel . configure all selected events for kernel space

perf top
  -p &lt;pid&gt; .. show stats for running process
  -F &lt;hz&gt; ... sampling frequency
  -K ........ hide kernel threads

perf record
  -p &lt;pid&gt; ............... record stats for running process
  -o &lt;file&gt; .............. write output to file (default perf.data)
  -F &lt;hz&gt; ................ sampling frequency
  --call-graph &lt;method&gt; .. [fp, dwarf, lbr] method how to caputre backtrace
                           fp   : use frame-pointer, need to compile with
                                  -fno-omit-frame-pointer
                           dwarf: use .cfi debug information
                           lbr  : use hardware last branch record facility
  -g ..................... short-hand for --call-graph fp
  -e &lt;ev&gt; ................ select event(s)
  --all-user ............. configure all selected events for user space
  --all-kernel ........... configure all selected events for kernel space
  -M intel ............... use intel disassembly in annotate

perf report
  -n .................... annotate symbols with nr of samples
  --stdio ............... report to stdio, if not presen tui mode
  -g graph,0.5,callee ... show callee based call chains with value &gt;0.5
</code></pre>
<pre><code>Useful &lt;ev&gt;:
  page-faults
  minor-faults
  major-faults
  cpu-cycles`
  task-clock
</code></pre>
<h2 id="select-specific-events"><a class="header" href="#select-specific-events">Select specific events</a></h2>
<p>Events to sample are specified with the <code>-e</code> option, either pass a comma
separated list or pass <code>-e</code> multiple times.</p>
<p>Events are specified in the following form <code>name[:modifier]</code>. The list and
description of the <code>modifier</code> can be found in the
<a href="https://man7.org/linux/man-pages/man1/perf-list.1.html"><code>perf-list(1)</code></a> manpage under <code>EVENT MODIFIERS</code>.</p>
<pre><code class="language-sh"># L1 i$ misses in user space
# L2 i$ stats in user/kernel space mixed
# Sample specified events.
perf stat -e L1-icache-load-misses:u \
          -e l2_rqsts.all_code_rd:uk,l2_rqsts.code_rd_hit:k,l2_rqsts.code_rd_miss:k \
          -- stress -c 2
</code></pre>
<p>The <code>--all-user</code> and <code>--all-kernel</code> options append a <code>:u</code> and <code>:k</code> modifier to
all specified events. Therefore the following two command lines are equivalent.</p>
<pre><code class="language-sh"># 1)
perf stat -e cycles:u,instructions:u -- ls

# 2)
perf stat --all-user -e cycles,instructions -- ls
</code></pre>
<h3 id="raw-events"><a class="header" href="#raw-events">Raw events</a></h3>
<p>In case perf does not provide a <em>symbolic</em> name for an event, the event can be
specified in a <em>raw</em> form as <code>r + UMask + EventCode</code>.</p>
<p>The following is an example for the <a href="https://github.com/intel/perfmon/blob/09c155f72e1b8f14b09aea346a35467a03a7d62b/SNB/events/sandybridge_core.json#L808">L2_RQSTS.CODE_RD_HIT</a> event
with <code>EventCode=0x24</code> and <code>UMask=0x10</code> on my laptop with a <code>sandybridge</code> uarch.</p>
<pre><code class="language-sh">perf stat -e l2_rqsts.code_rd_hit -e r1024 -- ls
# Performance counter stats for 'ls':
#
#       33.942      l2_rqsts.code_rd_hit
#       33.942      r1024
</code></pre>
<h3 id="find-raw-performance-counter-events-intel"><a class="header" href="#find-raw-performance-counter-events-intel">Find raw performance counter events (intel)</a></h3>
<p>The <a href="https://github.com/intel/perfmon"><code>intel/perfmon</code></a> repository provides a performance event
databases for the different intel uarchs.</p>
<p>The table in <a href="https://github.com/intel/perfmon/blob/main/mapfile.csv"><code>mapfile.csv</code></a> can be used to lookup the
corresponding uarch, just grab the family model from the procfs.</p>
<pre><code class="language-sh"> cat /proc/cpuinfo | awk '/^vendor_id/  { V=$3 }
                          /^cpu family/ { F=$4 }
                          /^model\s*:/  { printf "%s-%d-%x\n",V,F,$3 }'
</code></pre>
<blockquote>
<p>The table in <a href="https://github.com/intel/perfmon/tree/main#performance-monitoring-events">performance monitoring events</a> describes how
events are sorted into the different files.</p>
</blockquote>
<h3 id="raw-events-for-perfs-own-symbolic-names"><a class="header" href="#raw-events-for-perfs-own-symbolic-names">Raw events for perfs own symbolic names</a></h3>
<p>Perf also defines some own <em>symbolic</em> names for events. An example is the
<code>cache-references</code> event. The <a href="https://man7.org/linux/man-pages/man2/perf_event_open.2.html"><code>perf_event_open(2)</code></a> manpage
gives the following description.</p>
<pre><code class="language-man">perf_event_open(2)

PERF_COUNT_HW_CACHE_REFERENCES
    Cache accesses.  Usually this indicates Last Level Cache accesses but this
    may vary depending on your CPU.  This may include prefetches and coherency
    messages; again this depends on the design of your CPU.
</code></pre>
<p>The <code>sysfs</code> can be consulted to get the concrete performance counter on the
given system.</p>
<pre><code class="language-sh">cat /sys/devices/cpu/events/cache-misses
# event=0x2e,umask=0x41
</code></pre>
<h2 id="flamegraph"><a class="header" href="#flamegraph"><a href="https://github.com/brendangregg/FlameGraph"><code>Flamegraph</code></a></a></h2>
<h3 id="flamegraph-with-single-event-trace"><a class="header" href="#flamegraph-with-single-event-trace">Flamegraph with single event trace</a></h3>
<pre><code>perf record -g -e cpu-cycles -p &lt;pid&gt;
perf script | FlameGraph/stackcollapse-perf.pl | FlameGraph/flamegraph.pl &gt; cycles-flamegraph.svg
</code></pre>
<h3 id="flamegraph-with-multiple-event-traces"><a class="header" href="#flamegraph-with-multiple-event-traces">Flamegraph with multiple event traces</a></h3>
<pre><code class="language-sh">perf record -g -e cpu-cycles,page-faults -p &lt;pid&gt;
perf script --per-event-dump
# fold &amp; generate as above
</code></pre>
<h2 id="examples"><a class="header" href="#examples">Examples</a></h2>
<h3 id="estimate-max-instructions-per-cycle"><a class="header" href="#estimate-max-instructions-per-cycle">Estimate max instructions per cycle</a></h3>
<pre><code class="language-c">#define NOP4        "nop\nnop\nnop\nnop\n"
#define NOP32       NOP4   NOP4   NOP4   NOP4   NOP4   NOP4   NOP4   NOP4
#define NOP256      NOP32  NOP32  NOP32  NOP32  NOP32  NOP32  NOP32  NOP32
#define NOP2048     NOP256 NOP256 NOP256 NOP256 NOP256 NOP256 NOP256 NOP256

int main() {
  for (unsigned i = 0; i &lt; 2000000; ++i) {
    asm volatile(NOP2048);
  }
}
</code></pre>
<pre><code class="language-sh">perf stat -e cycles,instructions ./noploop
# Performance counter stats for './noploop':
#
#     1.031.075.940      cycles
#     4.103.534.341      instructions       #    3,98  insn per cycle
</code></pre>
<h3 id="caller-vs-callee-callstacks"><a class="header" href="#caller-vs-callee-callstacks">Caller vs callee callstacks</a></h3>
<p>The following gives an example for a scenario where we have the following calls</p>
<ul>
<li><code>main -&gt; do_foo() -&gt; do_work()</code></li>
<li><code>main -&gt; do_bar() -&gt; do_work()</code></li>
</ul>
<pre><code class="language-sh">perf report --stdio -g graph,callee

# Children      Self  Command  Shared Object         Symbols
# ........  ........  .......  ....................  .................
#
#  49.71%    49.66%   bench    bench                 [.] do_work
#          |
#           --49.66%--_start                &lt;- callstack bottom
#                     __libc_start_main
#                     0x7ff366c62ccf
#                     main
#                     |
#                     |--25.13%--do_bar
#                     |          do_work    &lt;- callstack top
#                     |
#                      --24.53%--do_foo
#                                do_work

perf report --stdio -g graph,callee

# Children      Self  Command  Shared Object         Symbols
# ........  ........  .......  ....................  .................
#
#  49.71%    49.66%   bench    bench                 [.] do_work
#          |
#          ---do_work                       &lt;- callstack top
#             |
#             |--25.15%--do_bar
#             |          main
#             |          0x7ff366c62ccf
#             |          __libc_start_main
#             |          _start             &lt;- callstack bottom
#             |
#              --24.55%--do_foo
#                        main
#                        0x7ff366c62ccf
#                        __libc_start_main
#                        _start             &lt;- callstack bottom
</code></pre>
<h2 id="references"><a class="header" href="#references">References</a></h2>
<ul>
<li><a href="https://github.com/intel/perfmon">intel/perfmon</a> - intel PMU event database per uarch</li>
<li><a href="https://perfmon-events.intel.com/">intel/perfmon-html</a> - a html rendered version of the PMU
events with search</li>
<li><a href="https://github.com/intel/perfmon/blob/main/mapfile.csv">intel/perfmon/mapfile.csv</a> - processor family to uarch mapping</li>
<li><a href="https://github.com/torvalds/linux/tree/master/tools/perf/pmu-events/arch/x86">linux/perf/events</a> - x86 PMU events known to perf tools</li>
<li><a href="https://github.com/torvalds/linux/blob/master/arch/x86/events/intel/core.c">linux/arch/events</a> - x86 PMU events linux kernel</li>
<li><a href="https://en.wikichip.org/wiki/WikiChip">wikichip</a> - computer architecture wiki</li>
<li><a href="https://man7.org/linux/man-pages/man1/perf-list.1.html">perf-list(1)</a> - manpage</li>
<li><a href="https://man7.org/linux/man-pages/man2/perf_event_open.2.html">perf_event_open(2)</a> - manpage</li>
<li><a href="https://www.intel.com/content/www/us/en/developer/articles/technical/intel-sdm.html">intel/sdm</a> - intel software developer manuals (eg Optimization
Reference Manual)</li>
</ul>

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