We have some infrastructure to use perl or python to analyze logs
generated by perf. Prior to this patch, only the python tools had
access to backtrace information. This patch makes this information
available to perl scripts as well. Example:
Let's look at malloc() calls made by the seq utility. First we
create a probe point:
$ perf probe -x /lib/x86_64-linux-gnu/libc.so.6 malloc
Added new events:
...
Now we run seq, while monitoring malloc() calls with perf
$ perf record --call-graph=dwarf -e probe_libc:malloc seq 5
1
2
3
4
5
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.064 MB perf.data (6 samples) ]
We can use perf to look at its log to see the malloc calls and the backtrace
$ perf script
seq 14195 [000] 1927993.748254: probe_libc:malloc: (7f9ff8edd320) bytes=0x22
7f9ff8edd320 malloc (/lib/x86_64-linux-gnu/libc-2.22.so)
7f9ff8e8eab0 set_binding_values.part.0 (/lib/x86_64-linux-gnu/libc-2.22.so)
7f9ff8e8eda1 __bindtextdomain (/lib/x86_64-linux-gnu/libc-2.22.so)
401b22 main (/usr/bin/seq)
7f9ff8e82610 __libc_start_main (/lib/x86_64-linux-gnu/libc-2.22.so)
402799 _start (/usr/bin/seq)
...
We can also use the scripting facilities. We create a skeleton perl
script that simply prints out the events
$ perf script -g perl
generated Perl script: perf-script.pl
We can then use this script to see the malloc() calls with a
backtrace. Prior to this patch, the backtrace was not available to
the perl scripts.
$ perf script -s perf-script.pl
probe_libc::malloc 0 1927993.748254260 14195 seq __probe_ip=140325052863264, bytes=34
[7f9ff8edd320] malloc
[7f9ff8e8eab0] set_binding_values.part.0
[7f9ff8e8eda1] __bindtextdomain
[401b22] main
[7f9ff8e82610] __libc_start_main
[402799] _start
...
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: http://lkml.kernel.org/r/87mvphzld0.fsf@secretsauce.net
Signed-off-by: Dima Kogan <dima@secretsauce.net>
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