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On one hand this ensures that the memory is properly freed when the DSO
gets freed. On the other hand this significantly speeds up the
processing of the callchain nodes when lots of srclines are requested.
For one of my data files e.g.:
Before:
Performance counter stats for 'perf report -s srcline -g srcline --stdio':
52496.495043 task-clock (msec) # 0.999 CPUs utilized
634 context-switches # 0.012 K/sec
2 cpu-migrations # 0.000 K/sec
191,561 page-faults # 0.004 M/sec
165,074,498,235 cycles # 3.144 GHz
334,170,832,408 instructions # 2.02 insn per cycle
90,220,029,745 branches # 1718.591 M/sec
654,525,177 branch-misses # 0.73% of all branches
52.533273822 seconds time elapsedProcessed 236605 events and lost 40 chunks!
After:
Performance counter stats for 'perf report -s srcline -g srcline --stdio':
22606.323706 task-clock (msec) # 1.000 CPUs utilized
31 context-switches # 0.001 K/sec
0 cpu-migrations # 0.000 K/sec
185,471 page-faults # 0.008 M/sec
71,188,113,681 cycles # 3.149 GHz
133,204,943,083 instructions # 1.87 insn per cycle
34,886,384,979 branches # 1543.214 M/sec
278,214,495 branch-misses # 0.80% of all branches
22.609857253 seconds time elapsed
Note that the difference is only this large when `--inline` is not
passed. In such situations, we would use the inliner cache and thus do
not run this code path that often.
I think that this cache should actually be used in other places, too.
When looking at the valgrind leak report for perf report, we see tons of
srclines being leaked, most notably from calls to
hist_entry__get_srcline. The problem is that get_srcline has many
different formatting options (show_sym, show_addr, potentially even
unwind_inlines when calling __get_srcline directly). As such, the
srcline cannot easily be cached for all calls, or we'd have to add
caches for all formatting combinations (6 so far). An alternative would
be to remove the formatting options and handle that on a different level
- i.e. print the sym/addr on demand wherever we actually output
something. And the unwind_inlines could be moved into a separate
function that does not return the srcline.
Signed-off-by: Milian Wolff <milian.wolff@kdab.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171019113836.5548-4-milian.wolff@kdab.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
21ac9d547f