linux-kernel - [PATCH 4/4] perf kvm: fix bug resolving guest kernel syms

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Message-Id: <1341956894-69284-5-git-send-email-dsahern@gmail.com>
Date:	Tue, 10 Jul 2012 15:48:14 -0600
From:	David Ahern <dsahern@...il.com>
To:	acme@...stprotocols.net, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	David Ahern <dsahern@...il.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	Jiri Olsa <jolsa@...hat.com>,
	Namhyung Kim <namhyung@...il.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH 4/4] perf kvm: fix bug resolving guest kernel syms

Guest kernel symbols are not resolved despite passing the information
needed to resolve them. e.g.,

perf kvm --guest --guestmount=/tmp/guest-mount record -a -- sleep 1
perf kvm --guest --guestmount=/tmp/guest-mount report --stdio

    36.55%  [guest/11399]  [unknown]         [g] 0xffffffff81600bc8
    33.19%  [guest/10474]  [unknown]         [g] 0x00000000c0116e00
    30.26%  [guest/11094]  [unknown]         [g] 0xffffffff8100a288

    43.69%  [guest/10474]  [unknown]         [g] 0x00000000c0103d90
    37.38%  [guest/11399]  [unknown]         [g] 0xffffffff81600bc8
    12.24%  [guest/11094]  [unknown]         [g] 0xffffffff810aa91d
     6.69%  [guest/11094]  [unknown]         [u] 0x00007fa784d721c3

which is just pathetic.

After a maddening 2 days sifting through perf minutia I found it --
id_hdr_size is not initialized for guest machines. This shows up on the
report side as random garbage for the cpu and timestamp, e.g.,

29816 7310572949125804849 0x1ac0 [0x50]: PERF_RECORD_MMAP ...

that messes up the sample sorting such that synthesized guest maps are
processed last.

With this patch you get a much more helpful report:

  12.11%  [guest/11399]  [guest.kernel.kallsyms.11399]  [g] irqtime_account_process_tick
  10.58%  [guest/11399]  [guest.kernel.kallsyms.11399]  [g] run_timer_softirq
   6.95%  [guest/11094]  [guest.kernel.kallsyms.11094]  [g] printk_needs_cpu
   6.50%  [guest/11094]  [guest.kernel.kallsyms.11094]  [g] do_timer
   6.45%  [guest/11399]  [guest.kernel.kallsyms.11399]  [g] idle_balance
   4.90%  [guest/11094]  [guest.kernel.kallsyms.11094]  [g] native_read_tsc
...

Signed-off-by: David Ahern <dsahern@...il.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...il.com>
Cc: Frederic Weisbecker <fweisbec@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
---
 tools/perf/util/map.c     |   24 ++++++++++++++++++++++++
 tools/perf/util/map.h     |    1 +
 tools/perf/util/session.c |    1 +
 3 files changed, 26 insertions(+)

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index 641377e..da3411b 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -730,3 +730,27 @@ char *machine__mmap_name(struct machine *self, char *bf, size_t size)
 
 	return bf;
 }
+
+void machines__set_id_hdr_size(struct rb_root *self, u16 id_hdr_size)
+{
+	struct rb_node *p;
+	struct machine *machine;
+
+    p = self->rb_node;
+	while (p != NULL) {
+		machine = rb_entry(p, struct machine, rb_node);
+		machine->id_hdr_size = id_hdr_size;
+        p = rb_next(p);
+	}
+
+    p = self->rb_node;
+    if (p)
+        p = rb_prev(p);
+	while (p != NULL) {
+		machine = rb_entry(p, struct machine, rb_node);
+		machine->id_hdr_size = id_hdr_size;
+        p = rb_prev(p);
+	}
+
+	return;
+}
diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
index 81371ba..7159b3c 100644
--- a/tools/perf/util/map.h
+++ b/tools/perf/util/map.h
@@ -151,6 +151,7 @@ struct machine *machines__add(struct rb_root *self, pid_t pid,
 struct machine *machines__find_host(struct rb_root *self);
 struct machine *machines__find(struct rb_root *self, pid_t pid);
 struct machine *machines__findnew(struct rb_root *self, pid_t pid);
+void machines__set_id_hdr_size(struct rb_root *self, u16 id_hdr_size);
 char *machine__mmap_name(struct machine *self, char *bf, size_t size);
 int machine__init(struct machine *self, const char *root_dir, pid_t pid);
 void machine__exit(struct machine *self);
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index 7c31623..fcf9498 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -86,6 +86,7 @@ void perf_session__update_sample_type(struct perf_session *self)
 	self->sample_id_all = perf_evlist__sample_id_all(self->evlist);
 	self->id_hdr_size = perf_evlist__id_hdr_size(self->evlist);
 	self->host_machine.id_hdr_size = self->id_hdr_size;
+    machines__set_id_hdr_size(&self->machines, self->id_hdr_size);
 }
 
 int perf_session__create_kernel_maps(struct perf_session *self)
-- 
1.7.10.1

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