Messages in this thread | | | Date | Fri, 11 Jul 2014 17:36:41 +0300 | From | Adrian Hunter <> | Subject | perf tools: Call graph from Intel BTS |
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Hi
Alexander Shishkin is working on the Intel PT driver for perf and has included a driver for Intel BTS. I have taken that and extended perf tools to enable the creation of context-sensitive call graphs. A screen shot from an example call graph from tracing "ls" is shown here:
http://git.infradead.org/~ahunter/call-graph-bts-ls.png
The patches are here:
http://git.infradead.org/users/ahunter/linux-perf.git
There are many perf tools patches and it would be helpful to start considering how to get them into mainline. Many need to wait for the driver, but others could be taken sooner.
The perf tools python API has been extended to facilitate exporting to databases, a script is provided to export to PostgreSQL, and another script reads the database and displays the call graph.
The Intel BTS data provides branches (address from / to) but to create the call graph the type of instruction (call, return etc) is needed. That is found by reading the object code, but for the kernel that requires an accurate image. A copy of /proc/kcore is needed but it must be made under the same conditions as the trace. That has proven sufficiently awkward to warrant creating a script to do it.
Here is how the "ls" call graph was created:
$ sudo bash -c 'echo 0 > /proc/sys/kernel/kptr_restrict' $ sudo bash -c 'echo -1 > /proc/sys/kernel/perf_event_paranoid' $ sudo bash -c 'chmod go+rx /sys/kernel/debug' $ ~/libexec/perf-core/perf-with-kcore record bts_ls --per-thread -e intel_bts// -- ls Recording Using /home/ahunter/bin/perf perf version 3.16.rc2.linux.local.gaabf /home/ahunter/bin/perf record -o bts_ls/perf.data --per-thread -e intel_bts// -- ls CREDITS drivers ipc MAINTAINERS modules.order REPORTING-BUGS signing_key.priv tools vmlinux.o arch crypto firmware Kconfig Makefile Module.symvers samples signing_key.x509 usr x509.genkey block fs include kernel mm net scripts sound virt bts_ls COPYING Documentation init Kbuild lib modules.builtin README security System.map vmlinux [ perf record: Woken up 100 times to write data ] [ perf record: Captured and wrote 6.945 MB bts_ls/perf.data ] Copying kcore Done $ ~/libexec/perf-core/perf-with-kcore script bts_ls -s ~/libexec/perf-core/scripts/python/export-to-postgresql.py bts_ls branches calls Using /home/ahunter/bin/perf perf version 3.16.rc2.linux.local.gaabf /home/ahunter/bin/perf script -i bts_ls/perf.data --kallsyms=bts_ls/kcore_dir/kallsyms -s ~/libexec/perf-core/scripts/python/export-to-postgresql.py bts_ls branches calls 2014-07-11 15:13:38.313702 Creating database... 2014-07-11 15:13:39.150277 Writing to intermediate files... 2014-07-11 15:13:40.182816 Copying to database... 2014-07-11 15:13:41.776815 Removing intermediate files... 2014-07-11 15:13:41.783443 Adding primary keys 2014-07-11 15:13:44.290786 Adding foreign keys 2014-07-11 15:13:44.974865 Done $ ~/libexec/perf-core/scripts/python/call-graph-from-postgresql.py bts_ls $
Regards Adrian
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