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doc/dev/perf.rst
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Kefu Chai
doc/dev/perf: add doc on disabling -fomit-frame-pointer
30 авг 2017, 07:14
30 авг 2017, 07:14
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Using perf ========== Top:: sudo perf top -p `pidof ceph-osd` To capture some data with call graphs:: sudo perf record -p `pidof ceph-osd` -F 99 --call-graph dwarf -- sleep 60 To view by caller (where you can see what each top function calls):: sudo perf report --call-graph caller To view by callee (where you can see who calls each top function):: sudo perf report --call-graph callee :note: If the caller/callee views look the same you may be suffering from a kernel bug; upgrade to 4.8 or later. Common Issues ------------- Ceph use `RelWithDebInfo` as its default `CMAKE_BUILD_TYPE`. Hence `-O2 -g` is used to compile the tree in this case. And the `-O2` optimization level enables `-fomit-frame-pointer` by default. But this prevents stack profilers from accessing the complete stack information. So one can disable this option when launching `cmake` :: cmake -DCMAKE_CXX_FLAGS="-fno-omit-frame-pointer" or when building the tree:: make CMAKE_CXX_FLAGS="-fno-omit-frame-pointer" Flamegraphs ----------- First, get things set up:: cd ~/src git clone https://github.com/brendangregg/FlameGraph Run ceph, then record some perf data:: sudo perf record -p `pidof ceph-osd` -F 99 --call-graph dwarf -- sleep 60 Then generate the flamegraph:: sudo perf script | ~/src/FlameGraph/stackcollapse-perf.pl > /tmp/folded ~/src/FlameGraph/flamegraph.pl /tmp/folded > /tmp/perf.svg firefox /tmp/perf.svg