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