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perf intel-pt: Update documentation about using /proc/kcore 

Update documentation to reflect the advent of the --kcore option for
'perf record'.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200429150751.12570-10-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Adrian Hunter 2020-04-29 18:07:51 +03:00 committed by Arnaldo Carvalho de Melo
parent 43358d9dfb
commit 6dd912cbad
1 changed files with 9 additions and 9 deletions
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18
tools/perf/Documentation/perf-intel-pt.txt
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@ -69,22 +69,22 @@ And profiled with 'perf report' e.g.
To also trace kernel space presents a problem, namely kernel self-modifying
code. A fairly good kernel image is available in /proc/kcore but to get an
accurate image a copy of /proc/kcore needs to be made under the same conditions
as the data capture. A script perf-with-kcore can do that, but beware that the
script makes use of 'sudo' to copy /proc/kcore. If you have perf installed
locally from the source tree you can do:
as the data capture. 'perf record' can make a copy of /proc/kcore if the option
--kcore is used, but access to /proc/kcore is restricted e.g.
~/libexec/perf-core/perf-with-kcore record pt_ls -e intel_pt// -- ls
sudo perf record -o pt_ls --kcore -e intel_pt// -- ls
which will create a directory named 'pt_ls' and put the perf.data file and
copies of /proc/kcore, /proc/kallsyms and /proc/modules into it. Then to use
'perf report' becomes:
which will create a directory named 'pt_ls' and put the perf.data file (named
simply 'data') and copies of /proc/kcore, /proc/kallsyms and /proc/modules into
it. The other tools understand the directory format, so to use 'perf report'
becomes:
~/libexec/perf-core/perf-with-kcore report pt_ls
sudo perf report -i pt_ls
Because samples are synthesized after-the-fact, the sampling period can be
selected for reporting. e.g. sample every microsecond
~/libexec/perf-core/perf-with-kcore report pt_ls --itrace=i1usge
sudo perf report pt_ls --itrace=i1usge
See the sections below for more information about the --itrace option.