[PATCH 0/2] Fix perf-tool crashes when kvm guest is running

[PATCH 0/2] Fix perf-tool crashes when kvm guest is running

[Joerg Roedel]

Hi,

here are the fixes I promised. These patches should fix the crashes
David and Jason have seen by making sure no sample is processed when
ther is no valid machine object for it. The second patch also changes
the perf_guest default back to false.

Regards,

	Joerg

[PATCH 1/2] perf-tool: Don't process samples with no valid machine object

[Joerg Roedel]

The perf sample processing code relies on a valid machine
object. Make sure that this path is only entered when such a
object exists.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 tools/perf/builtin-top.c  |    2 +-
 tools/perf/util/session.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index dd162aa..7c81d1d 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -805,7 +805,7 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx)
 		}
 
 
-		if (event->header.type == PERF_RECORD_SAMPLE) {
+		if (event->header.type == PERF_RECORD_SAMPLE && machine != NULL) {
 			perf_event__process_sample(&top->tool, event, evsel,
 						   &sample, machine);
 		} else if (event->header.type < PERF_RECORD_MAX) {
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index b5ca2558..c9593c7 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -792,7 +792,7 @@ static int perf_session_deliver_event(struct perf_session *session,
 	switch (event->header.type) {
 	case PERF_RECORD_SAMPLE:
 		dump_sample(session, event, sample);
-		if (evsel == NULL) {
+		if (evsel == NULL || machine == NULL) {
 			++session->hists.stats.nr_unknown_id;
 			return -1;
 		}
-- 
1.7.5.4

[PATCH 2/2] perf-tool: Change perf_guest default back to false

[Joerg Roedel]

Setting perf_guest to true by default makes no sense because
the perf subcommands can not setup guest symbol information
and thus not process and guest samples. The only exception
is perf-kvm which changes the perf_guest value on its own.
So change the default for perf_guest back to false.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 tools/perf/util/util.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 8131410..fb25d13 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -6,7 +6,7 @@
  * XXX We need to find a better place for these things...
  */
 bool perf_host  = true;
-bool perf_guest = true;
+bool perf_guest = false;
 
 void event_attr_init(struct perf_event_attr *attr)
 {
-- 
1.7.5.4

Re: [PATCH 1/2] perf-tool: Don't process samples with no valid machine object

[Arnaldo Carvalho de Melo]

Em Thu, Feb 09, 2012 at 05:07:38PM +0100, Joerg Roedel escreveu:
> The perf sample processing code relies on a valid machine
> object. Make sure that this path is only entered when such a
> object exists.
> 
> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
> ---
>  tools/perf/builtin-top.c  |    2 +-
>  tools/perf/util/session.c |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
> index dd162aa..7c81d1d 100644
> --- a/tools/perf/builtin-top.c
> +++ b/tools/perf/builtin-top.c
> @@ -805,7 +805,7 @@ static void perf_top__mmap_read_idx(struct perf_top *top, int idx)
>  		}
>  
>  
> -		if (event->header.type == PERF_RECORD_SAMPLE) {
> +		if (event->header.type == PERF_RECORD_SAMPLE && machine != NULL) {

Shouldn't we warn the user, even if just once, on the status (last line
on the screen) line?

>  			perf_event__process_sample(&top->tool, event, evsel,
>  						   &sample, machine);
>  		} else if (event->header.type < PERF_RECORD_MAX) {
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index b5ca2558..c9593c7 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -792,7 +792,7 @@ static int perf_session_deliver_event(struct perf_session *session,
>  	switch (event->header.type) {
>  	case PERF_RECORD_SAMPLE:
>  		dump_sample(session, event, sample);
> -		if (evsel == NULL) {
> +		if (evsel == NULL || machine == NULL) {
>  			++session->hists.stats.nr_unknown_id;
>  			return -1;
>  		}
> -- 
> 1.7.5.4
> 

Re: [PATCH 1/2] perf-tool: Don't process samples with no valid machine object

[Joerg Roedel]

On Thu, Feb 09, 2012 at 02:34:41PM -0200, Arnaldo Carvalho de Melo wrote:
> Em Thu, Feb 09, 2012 at 05:07:38PM +0100, Joerg Roedel escreveu:
> > -		if (event->header.type == PERF_RECORD_SAMPLE) {
> > +		if (event->header.type == PERF_RECORD_SAMPLE && machine != NULL) {
> 
> Shouldn't we warn the user, even if just once, on the status (last line
> on the screen) line?

Probably yes, what would be a good message? I guess something like

	"no machine object for sample"

is not helpful to the user. Maybe something like

	"Unresolvable sample(s) recorded"?

Or something completly different?


	Joerg

-- 
AMD Operating System Research Center

Advanced Micro Devices GmbH Einsteinring 24 85609 Dornach
General Managers: Alberto Bozzo
Registration: Dornach, Landkr. Muenchen; Registerger. Muenchen, HRB Nr. 43632

Re: [PATCH 1/2] perf-tool: Don't process samples with no valid machine object

[Arnaldo Carvalho de Melo]

Em Thu, Feb 09, 2012 at 06:13:34PM +0100, Joerg Roedel escreveu:
> On Thu, Feb 09, 2012 at 02:34:41PM -0200, Arnaldo Carvalho de Melo wrote:
> > Em Thu, Feb 09, 2012 at 05:07:38PM +0100, Joerg Roedel escreveu:
> > > -		if (event->header.type == PERF_RECORD_SAMPLE) {
> > > +		if (event->header.type == PERF_RECORD_SAMPLE && machine != NULL) {
> > 
> > Shouldn't we warn the user, even if just once, on the status (last line
> > on the screen) line?
> 
> Probably yes, what would be a good message? I guess something like
> 
> 	"no machine object for sample"
> 
> is not helpful to the user. Maybe something like
> 
> 	"Unresolvable sample(s) recorded"?
> 
> Or something completly different?

This is not completely standardized or harminized across the sources,
but we have things like:

	if (verbose)
		error("Failed to resolve callchain.  Skipping\n");

---

        if (perf_event__preprocess_sample(event, machine, &al, sample,
                                          NULL) < 0) {
                error("problem processing %d event, skipping it.\n",
                        event->header.type);
                return;
        }

---

       if (!ip_callchain__valid(sample->callchain, event)) {
                pr_debug("call-chain problem with event, skipping it.\n");
                ++session->hists.stats.nr_invalid_chains;

---


	What has been done more recently is like the above, account the
number of different problems and then, at the end do like:

        if (session->hists.stats.nr_unknown_id != 0) {
                ui__warning("%u samples with id not present in the header\n",
                            session->hists.stats.nr_unknown_id);
        }


	But this is for perf report or other tools that process all
events and then provide some post processed results, just before
presenting these results.

	I guess we could do that too for 'perf top' like tools, that
continuously show results while collecting more. Perhaps call
ui__warning() if some threshold happens, i.e. if way too many errors of
some kind are happening and then at the end provide a summary of errors
found.

- Arnaldo

[PATCH 1/2] perf-tool: Don't process samples with no valid machine object

[Joerg Roedel]

The perf sample processing code relies on a valid machine
object. Make sure that this path is only entered when such a
object exists.

A counter for samples where no machine object exits is also
introduced to give the user a message about these samples.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
---
 tools/perf/builtin-top.c  |    6 ++++++
 tools/perf/util/hist.h    |    1 +
 tools/perf/util/session.c |   10 ++++++++++
 3 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index dd162aa..48e0090 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -668,6 +668,12 @@ static void perf_event__process_sample(struct perf_tool *tool,
 		return;
 	}
 
+	if (!machine) {
+		pr_err("%u unprocessable samples recorded.",
+		       top->session->hists.stats.nr_unprocessable_samples++);
+		return;
+	}
+
 	if (event->header.misc & PERF_RECORD_MISC_EXACT_IP)
 		top->exact_samples++;
 
diff --git a/tools/perf/util/hist.h b/tools/perf/util/hist.h
index f55f0a8d..8d5641f 100644
--- a/tools/perf/util/hist.h
+++ b/tools/perf/util/hist.h
@@ -32,6 +32,7 @@ struct events_stats {
 	u32 nr_unknown_events;
 	u32 nr_invalid_chains;
 	u32 nr_unknown_id;
+	u32 nr_unprocessable_samples;
 };
 
 enum hist_column {
diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
index b5ca2558..a8d25d9 100644
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c
@@ -796,6 +796,10 @@ static int perf_session_deliver_event(struct perf_session *session,
 			++session->hists.stats.nr_unknown_id;
 			return -1;
 		}
+		if (machine == NULL) {
+			++session->hists.stats.nr_unprocessable_samples;
+			return -1;
+		}
 		return tool->sample(tool, event, sample, evsel, machine);
 	case PERF_RECORD_MMAP:
 		return tool->mmap(tool, event, sample, machine);
@@ -964,6 +968,12 @@ static void perf_session__warn_about_errors(const struct perf_session *session,
  			    session->hists.stats.nr_invalid_chains,
  			    session->hists.stats.nr_events[PERF_RECORD_SAMPLE]);
  	}
+
+	if (session->hists.stats.nr_unprocessable_samples != 0) {
+		ui__warning("%u unprocessable samples recorded.\n"
+			    "Do you have a KVM guest running and not using 'perf kvm'?\n",
+			    session->hists.stats.nr_unprocessable_samples);
+	}
 }
 
 #define session_done()	(*(volatile int *)(&session_done))
-- 
1.7.5.4