3.16.82-rc1 review patch. If anyone has any objections, please let me know.
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From: Masami Hiramatsu mhiramat@kernel.org
commit f4d99bdfd124823a81878b44b5e8750b97f73902 upstream.
Skip end-of-sequence and non-statement lines while walking through lines list.
The "end-of-sequence" line information means:
"the current address is that of the first byte after the end of a sequence of target machine instructions." (DWARF version 4 spec 6.2.2)
This actually means out of scope and we can not probe on it.
On the other hand, the statement lines (is_stmt) means:
"the current instruction is a recommended breakpoint location. A recommended breakpoint location is intended to “represent” a line, a statement and/or a semantically distinct subpart of a statement."
(DWARF version 4 spec 6.2.2)
So, non-statement line info also should be skipped.
These can reduce unneeded probe points and also avoid an error.
E.g. without this patch:
# perf probe -a "clear_tasks_mm_cpumask:1" Added new events: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_1 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_2 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_3 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_4 (on clear_tasks_mm_cpumask:1)
You can now use it in all perf tools, such as:
perf record -e probe:clear_tasks_mm_cpumask_4 -aR sleep 1
#
This puts 5 probes on one line, but acutally it's not inlined function. This is because there are many non statement instructions at the function prologue.
With this patch:
# perf probe -a "clear_tasks_mm_cpumask:1" Added new event: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1)
You can now use it in all perf tools, such as:
perf record -e probe:clear_tasks_mm_cpumask -aR sleep 1
#
Now perf-probe skips unneeded addresses.
Committer testing:
Slightly different results, but similar:
Before:
# uname -a Linux quaco 5.3.8-200.fc30.x86_64 #1 SMP Tue Oct 29 14:46:22 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux # # perf probe -a "clear_tasks_mm_cpumask:1" Added new events: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_1 (on clear_tasks_mm_cpumask:1) probe:clear_tasks_mm_cpumask_2 (on clear_tasks_mm_cpumask:1)
You can now use it in all perf tools, such as:
perf record -e probe:clear_tasks_mm_cpumask_2 -aR sleep 1
#
After:
# perf probe -a "clear_tasks_mm_cpumask:1" Added new event: probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask:1)
You can now use it in all perf tools, such as:
perf record -e probe:clear_tasks_mm_cpumask -aR sleep 1
# perf probe -l probe:clear_tasks_mm_cpumask (on clear_tasks_mm_cpumask@kernel/cpu.c) #
Fixes: 4cc9cec636e7 ("perf probe: Introduce lines walker interface") Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Tested-by: Arnaldo Carvalho de Melo acme@redhat.com Cc: Jiri Olsa jolsa@redhat.com Cc: Namhyung Kim namhyung@kernel.org Link: http://lore.kernel.org/lkml/157241936090.32002.12156347518596111660.stgit@de... Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- tools/perf/util/dwarf-aux.c | 7 +++++++ 1 file changed, 7 insertions(+)
--- a/tools/perf/util/dwarf-aux.c +++ b/tools/perf/util/dwarf-aux.c @@ -712,6 +712,7 @@ int die_walk_lines(Dwarf_Die *rt_die, li int decl = 0, inl; Dwarf_Die die_mem, *cu_die; size_t nlines, i; + bool flag;
/* Get the CU die */ if (dwarf_tag(rt_die) != DW_TAG_compile_unit) { @@ -742,6 +743,12 @@ int die_walk_lines(Dwarf_Die *rt_die, li "Possible error in debuginfo.\n"); continue; } + /* Skip end-of-sequence */ + if (dwarf_lineendsequence(line, &flag) != 0 || flag) + continue; + /* Skip Non statement line-info */ + if (dwarf_linebeginstatement(line, &flag) != 0 || !flag) + continue; /* Filter lines based on address */ if (rt_die != cu_die) { /*