ceph/doc/dev/perf.rst

   1 Using perf
   2 ==========
   3
   4 Top::
   5
   6   sudo perf top -p `pidof ceph-osd`
   7
   8 To capture some data with call graphs::
   9
  10   sudo perf record -p `pidof ceph-osd` -F 99 --call-graph dwarf -- sleep 60
  11
  12 To view by caller (where you can see what each top function calls)::
  13
  14   sudo perf report --call-graph caller
  15
  16 To view by callee (where you can see who calls each top function)::
  17
  18   sudo perf report --call-graph callee
  19
  20 :note: If the caller/callee views look the same you may be
  21        suffering from a kernel bug; upgrade to 4.8 or later.
  22
  23 Common Issues
  24 -------------
  25
  26 Ceph use `RelWithDebInfo` as its default `CMAKE_BUILD_TYPE`. Hence `-O2 -g` is
  27 used to compile the tree in this case. And the `-O2` optimization level
  28 enables `-fomit-frame-pointer` by default. But this prevents stack profilers
  29 from accessing the complete stack information. So one can disable this option
  30 when launching `cmake` ::
  31
  32   cmake -DCMAKE_CXX_FLAGS="-fno-omit-frame-pointer"
  33
  34 or when building the tree::
  35
  36   make CMAKE_CXX_FLAGS="-fno-omit-frame-pointer"
  37
  38
  39 Flamegraphs
  40 -----------
  41
  42 First, get things set up::
  43
  44   cd ~/src
  45   git clone https://github.com/brendangregg/FlameGraph
  46
  47 Run ceph, then record some perf data::
  48
  49   sudo perf record -p `pidof ceph-osd` -F 99 --call-graph dwarf -- sleep 60
  50
  51 Then generate the flamegraph::
  52
  53   sudo perf script | ~/src/FlameGraph/stackcollapse-perf.pl > /tmp/folded
  54   ~/src/FlameGraph/flamegraph.pl /tmp/folded > /tmp/perf.svg
  55   firefox /tmp/perf.svg