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Subject[PATCH v3 3/3] perf-top: add --max-stack option to limit callchain stack scan
Date
When the callgraph function is enabled (-G), it may take a long time to
scan all the stack data and merge them accordingly.

This patch adds a new --max-stack option to perf-top to limit the depth
of callchain stack data to look at to reduce the time it takes for
perf-top to finish its processing. It reduces the amount of information
provided to the user in exchange for faster speed.

Signed-off-by: Waiman Long <Waiman.Long@hp.com>
Acked-by: David Ahern <dsahern@gmail.com>
Tested-by: Davidlohr Bueso <davidlohr@hp.com>
---
tools/perf/Documentation/perf-top.txt | 8 ++++++++
tools/perf/builtin-top.c | 8 ++++++--
tools/perf/util/top.h | 1 +
3 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 58d6598..3fd911c 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -155,6 +155,14 @@ Default is to monitor all CPUS.

Default: fractal,0.5,callee.

+--max-stack::
+ Set the stack depth limit when parsing the callchain, anything
+ beyond the specified depth will be ignored. This is a trade-off
+ between information loss and faster processing especially for
+ workloads that can have a very long callchain stack.
+
+ Default: 127
+
--ignore-callees=<regex>::
Ignore callees of the function(s) matching the given regex.
This has the effect of collecting the callers of each such
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 2725aca..14902b0 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -772,7 +772,7 @@ static void perf_event__process_sample(struct perf_tool *tool,
err = machine__resolve_callchain(machine, evsel,
al.thread, sample,
&parent, &al,
- PERF_MAX_STACK_DEPTH);
+ top->max_stack);
if (err)
return;
}
@@ -1052,10 +1052,11 @@ int cmd_top(int argc, const char **argv, const char *prefix __maybe_unused)
.user_freq = UINT_MAX,
.user_interval = ULLONG_MAX,
.freq = 4000, /* 4 KHz */
- .target = {
+ .target = {
.uses_mmap = true,
},
},
+ .max_stack = PERF_MAX_STACK_DEPTH,
.sym_pcnt_filter = 5,
};
struct perf_record_opts *opts = &top.record_opts;
@@ -1110,6 +1111,9 @@ int cmd_top(int argc, const char **argv, const char *prefix __maybe_unused)
OPT_CALLBACK_DEFAULT('G', "call-graph", &top.record_opts,
"mode[,dump_size]", record_callchain_help,
&parse_callchain_opt, "fp"),
+ OPT_INTEGER(0, "max-stack", &top.max_stack,
+ "Set the maximum stack depth when parsing the callchain. "
+ "Default: " __stringify(PERF_MAX_STACK_DEPTH)),
OPT_CALLBACK(0, "ignore-callees", NULL, "regex",
"ignore callees of these functions in call graphs",
report_parse_ignore_callees_opt),
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index b554ffc..88cfeaf 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -24,6 +24,7 @@ struct perf_top {
u64 exact_samples;
u64 guest_us_samples, guest_kernel_samples;
int print_entries, count_filter, delay_secs;
+ int max_stack;
bool hide_kernel_symbols, hide_user_symbols, zero;
bool use_tui, use_stdio;
bool kptr_restrict_warned;
--
1.7.1


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