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From: kan.liang@linux.intel.com
To: peterz@infradead.org, acme@redhat.com, mingo@kernel.org,
	linux-kernel@vger.kernel.org
Cc: jolsa@kernel.org, namhyung@kernel.org,
	vitaly.slobodskoy@intel.com, pavel.gerasimov@intel.com,
	ak@linux.intel.com, eranian@google.com, mpe@ellerman.id.au,
	Kan Liang <kan.liang@linux.intel.com>
Subject: [PATCH V4 11/13] perf top: Add option to enable the LBR stitching approach
Date: Tue, 19 Nov 2019 06:34:09 -0800	[thread overview]
Message-ID: <20191119143411.3482-12-kan.liang@linux.intel.com> (raw)
In-Reply-To: <20191119143411.3482-1-kan.liang@linux.intel.com>

From: Kan Liang <kan.liang@linux.intel.com>

With the LBR stitching approach, the reconstructed LBR call stack
can break the HW limitation. However, it may reconstruct invalid call
stacks in some cases, e.g. exception handing such as setjmp/longjmp.
Also, it may impact the processing time especially when the number of
samples with stitched LBRs are huge.

Add an option to enable the approach.
The option must be used with --call-graph lbr.

Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
 tools/perf/Documentation/perf-top.txt |  9 +++++++++
 tools/perf/builtin-top.c              | 11 +++++++++++
 tools/perf/util/top.h                 |  1 +
 3 files changed, 21 insertions(+)

diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 5596129a71cf..80b57f942a86 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -304,6 +304,15 @@ Default is to monitor all CPUS.
 	go straight to the histogram browser, just like 'perf top' with no events
 	explicitely specified does.
 
+--stitch-lbr::
+	Show callgraph with stitched LBRs, which may have more complete
+	callgraph. The option must be used with --call-graph lbr recording.
+	Disabled by default. In common cases with call stack overflows,
+	it can recreate better call stacks than the default lbr call stack
+	output. But this approach is not full proof. There can be cases
+	where it creates incorrect call stacks from incorrect matches.
+	The known limitations include exception handing such as
+	setjmp/longjmp will have calls/returns not match.
 
 INTERACTIVE PROMPTING KEYS
 --------------------------
diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index dc80044bc46f..7c820cfe2f23 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -33,6 +33,7 @@
 #include "util/map.h"
 #include "util/mmap.h"
 #include "util/session.h"
+#include "util/thread.h"
 #include "util/symbol.h"
 #include "util/synthetic-events.h"
 #include "util/top.h"
@@ -766,6 +767,9 @@ static void perf_event__process_sample(struct perf_tool *tool,
 	if (machine__resolve(machine, &al, sample) < 0)
 		return;
 
+	if (top->stitch_lbr)
+		al.thread->lbr_stitch_enable = true;
+
 	if (!machine->kptr_restrict_warned &&
 	    symbol_conf.kptr_restrict &&
 	    al.cpumode == PERF_RECORD_MISC_KERNEL) {
@@ -1539,6 +1543,8 @@ int cmd_top(int argc, const char **argv)
 			"number of thread to run event synthesize"),
 	OPT_BOOLEAN(0, "namespaces", &opts->record_namespaces,
 		    "Record namespaces events"),
+	OPT_BOOLEAN(0, "stitch-lbr", &top.stitch_lbr,
+		    "Enable LBR callgraph stitching approach"),
 	OPTS_EVSWITCH(&top.evswitch),
 	OPT_END()
 	};
@@ -1601,6 +1607,11 @@ int cmd_top(int argc, const char **argv)
 		}
 	}
 
+	if (top.stitch_lbr && !(callchain_param.record_mode == CALLCHAIN_LBR)) {
+		pr_err("Error: --stitch-lbr must be used with --call-graph lbr\n");
+		goto out_delete_evlist;
+	}
+
 	if (opts->branch_stack && callchain_param.enabled)
 		symbol_conf.show_branchflag_count = true;
 
diff --git a/tools/perf/util/top.h b/tools/perf/util/top.h
index f117d4f4821e..45dc84ddff37 100644
--- a/tools/perf/util/top.h
+++ b/tools/perf/util/top.h
@@ -36,6 +36,7 @@ struct perf_top {
 	bool		   use_tui, use_stdio;
 	bool		   vmlinux_warned;
 	bool		   dump_symtab;
+	bool		   stitch_lbr;
 	struct hist_entry  *sym_filter_entry;
 	struct evsel 	   *sym_evsel;
 	struct perf_session *session;
-- 
2.17.1


  parent reply	other threads:[~2019-11-19 14:35 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-19 14:33 [PATCH V4 00/13] Stitch LBR call stack kan.liang
2019-11-19 14:33 ` [PATCH V4 01/13] perf/core: Add new branch sample type for LBR TOS kan.liang
2019-11-19 19:02   ` Stephane Eranian
2019-11-19 22:25     ` Liang, Kan
2019-11-19 22:51       ` Stephane Eranian
2019-11-20 15:06         ` Liang, Kan
2019-11-19 14:34 ` [PATCH V4 02/13] perf/x86/intel: Output LBR TOS information kan.liang
2019-11-19 14:34 ` [PATCH V4 03/13] perf tools: Support new branch sample type for LBR TOS kan.liang
2019-11-19 19:00   ` Stephane Eranian
2019-11-19 21:31     ` Peter Zijlstra
2019-11-19 22:17       ` Liang, Kan
2019-11-19 14:34 ` [PATCH V4 04/13] perf header: Add check for event attr kan.liang
2019-11-19 14:34 ` [PATCH V4 05/13] perf pmu: Add support for PMU capabilities kan.liang
2019-11-19 14:34 ` [PATCH V4 06/13] perf header: Support CPU " kan.liang
2019-11-19 14:34 ` [PATCH V4 07/13] perf machine: Refine the function for LBR call stack reconstruction kan.liang
2019-11-19 14:34 ` [PATCH V4 08/13] perf tools: Stitch LBR call stack kan.liang
2019-11-19 14:34 ` [PATCH V4 09/13] perf report: Add option to enable the LBR stitching approach kan.liang
2019-11-19 14:34 ` [PATCH V4 10/13] perf script: " kan.liang
2019-11-19 14:34 ` kan.liang [this message]
2019-11-19 14:34 ` [PATCH V4 12/13] perf c2c: " kan.liang
2019-11-19 14:34 ` [RFC PATCH V4 13/13] perf hist: Add fast path for duplicate entries check approach kan.liang

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