[PATCH] perf script python: Fix buffer size to report iregs in perf script

Commit 48a1f565261d ("perf script python: Add more PMU fields
to event handler dict") added functionality to report fields like
weight, iregs, uregs etc via perf report.
That commit predefined buffer size to 512 bytes to print those fields.

But incase of powerpc, since we added extended regs support
in commits:

Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Commit d735599a069f ("powerpc/perf: Add extended regs support for
power10 platform")

Now iregs can carry more bytes of data and this predefined buffer size
can result to data loss in perf script output.

Patch resolve this issue by making buffer size dynamic based on number
of registers needed to print. It also changed return type for function
"regs_map" from int to void, as the return value is not being used by
the caller function "set_regs_in_dict".

Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Signed-off-by: Kajol Jain <redacted>
---
 .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 4e4aa4c97ac5..c8c9706b4643 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c

@@ -687,7 +687,7 @@ static void set_sample_datasrc_in_dict(PyObject *dict,
 			_PyUnicode_FromString(decode));
 }
 
-static int regs_map(struct regs_dump *regs, uint64_t mask, char *bf, int size)
+static void regs_map(struct regs_dump *regs, uint64_t mask, char *bf, int size)
 {
 	unsigned int i = 0, r;
 	int printed = 0;

@@ -695,7 +695,7 @@ static int regs_map(struct regs_dump *regs, uint64_t mask, char *bf, int size)
 	bf[0] = 0;
 
 	if (!regs || !regs->regs)
-		return 0;
+		return;
 
 	for_each_set_bit(r, (unsigned long *) &mask, sizeof(mask) * 8) {
 		u64 val = regs->regs[i++];

@@ -704,8 +704,6 @@ static int regs_map(struct regs_dump *regs, uint64_t mask, char *bf, int size)
 				     "%5s:0x%" PRIx64 " ",
 				     perf_reg_name(r), val);
 	}
-
-	return printed;
 }
 
 static void set_regs_in_dict(PyObject *dict,

@@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict,
 			     struct evsel *evsel)
 {
 	struct perf_event_attr *attr = &evsel->core.attr;
-	char bf[512];
+
+	/*
+	 * Here value 28 is a constant size which can be used to print
+	 * one register value and its corresponds to:
+	 * 16 chars is to specify 64 bit register in hexadecimal.
+	 * 2 chars is for appending "0x" to the hexadecimal value and
+	 * 10 chars is for register name.
+	 */
+	int size = __sw_hweight64(attr->sample_regs_intr) * 28;
+	char bf[size];
 
 	regs_map(&sample->intr_regs, attr->sample_regs_intr, bf, sizeof(bf));
 

-- 
2.31.1

Tested by creating perf-script.py using perf script
and priting the iregs. Seen more values with this patch.


Tested-by: Nageswara R Sastry <redacted>

On 28/06/21 11:53 am, Kajol Jain wrote:

-- 
Thanks and Regards
R.Nageswara Sastry

On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote:

[...]

I propose using a template rather than a magic number here. Something like:
const char reg_name_tmpl[] = "10 chars  ";
const char reg_value_tmpl[] = "0x0123456789abcdef";
const int size = __sw_hweight64(attr->sample_regs_intr) +
                 sizeof reg_name_tmpl + sizeof reg_value_tmpl;

Pardon my ignorance, but is there no separation/whitespace between the name
and the value? And is there some significance to 10 characters for the
register name, or is that a magic number?

PC

On 6/28/21 8:19 PM, Paul A. Clarke wrote:

On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote:

quoted

Commit 48a1f565261d ("perf script python: Add more PMU fields
to event handler dict") added functionality to report fields like
weight, iregs, uregs etc via perf report.
That commit predefined buffer size to 512 bytes to print those fields.

But incase of powerpc, since we added extended regs support
in commits:

Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Commit d735599a069f ("powerpc/perf: Add extended regs support for
power10 platform")

Now iregs can carry more bytes of data and this predefined buffer size
can result to data loss in perf script output.

Patch resolve this issue by making buffer size dynamic based on number
of registers needed to print. It also changed return type for function
"regs_map" from int to void, as the return value is not being used by
the caller function "set_regs_in_dict".

Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Signed-off-by: Kajol Jain <redacted>
---
 .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 4e4aa4c97ac5..c8c9706b4643 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c

[...]

quoted

@@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict,
 			     struct evsel *evsel)
 {
 	struct perf_event_attr *attr = &evsel->core.attr;
-	char bf[512];
+
+	/*
+	 * Here value 28 is a constant size which can be used to print
+	 * one register value and its corresponds to:
+	 * 16 chars is to specify 64 bit register in hexadecimal.
+	 * 2 chars is for appending "0x" to the hexadecimal value and
+	 * 10 chars is for register name.
+	 */
+	int size = __sw_hweight64(attr->sample_regs_intr) * 28;
+	char bf[size];

I propose using a template rather than a magic number here. Something like:
const char reg_name_tmpl[] = "10 chars  ";
const char reg_value_tmpl[] = "0x0123456789abcdef";
const int size = __sw_hweight64(attr->sample_regs_intr) +
                 sizeof reg_name_tmpl + sizeof reg_value_tmpl;

Hi Paul,
   Thanks for reviewing the patch. Yes these are
some standardization we can do by creating macros for different
fields.
The basic idea is, we want to provide significant buffer size
based on number of registers present in sample_regs_intr to accommodate
all data.

But before going to optimizing code, Arnaldo/Jiri, is this approach looks good to you?

Pardon my ignorance, but is there no separation/whitespace between the name
and the value?

This is how we will get data via perf script

r0:0xc000000000112008
r1:0xc000000023b37920
r2:0xc00000000144c900
r3:0xc0000000bc566120
r4:0xc0000000c5600000
r5:0x2606c6506ca
r6:0xc000000023b378f8
r7:0xfffffd9f93a48f0e
.....

 And is there some significance to 10 characters for the

register name, or is that a magic number?

Most of the register name are within 10 characters, basically we are giving this
magic number to make sure we have enough space in buffer to contain all registers
name with colon.

Thanks,
Kajol Jain
 

PC

On 6/29/21 12:39 PM, kajoljain wrote:

On 6/28/21 8:19 PM, Paul A. Clarke wrote:

quoted

On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote:

quoted

Commit 48a1f565261d ("perf script python: Add more PMU fields
to event handler dict") added functionality to report fields like
weight, iregs, uregs etc via perf report.
That commit predefined buffer size to 512 bytes to print those fields.

But incase of powerpc, since we added extended regs support
in commits:

Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Commit d735599a069f ("powerpc/perf: Add extended regs support for
power10 platform")

Now iregs can carry more bytes of data and this predefined buffer size
can result to data loss in perf script output.

Patch resolve this issue by making buffer size dynamic based on number
of registers needed to print. It also changed return type for function
"regs_map" from int to void, as the return value is not being used by
the caller function "set_regs_in_dict".

Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Signed-off-by: Kajol Jain <redacted>
---
 .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 4e4aa4c97ac5..c8c9706b4643 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c

[...]

quoted

@@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict,
 			     struct evsel *evsel)
 {
 	struct perf_event_attr *attr = &evsel->core.attr;
-	char bf[512];
+
+	/*
+	 * Here value 28 is a constant size which can be used to print
+	 * one register value and its corresponds to:
+	 * 16 chars is to specify 64 bit register in hexadecimal.
+	 * 2 chars is for appending "0x" to the hexadecimal value and
+	 * 10 chars is for register name.
+	 */
+	int size = __sw_hweight64(attr->sample_regs_intr) * 28;
+	char bf[size];

I propose using a template rather than a magic number here. Something like:
const char reg_name_tmpl[] = "10 chars  ";
const char reg_value_tmpl[] = "0x0123456789abcdef";
const int size = __sw_hweight64(attr->sample_regs_intr) +
                 sizeof reg_name_tmpl + sizeof reg_value_tmpl;

Hi Paul,
   Thanks for reviewing the patch. Yes these are
some standardization we can do by creating macros for different
fields.
The basic idea is, we want to provide significant buffer size
based on number of registers present in sample_regs_intr to accommodate
all data.

Hi Arnaldo/Jiri,
   Is the approach used in this patch looks fine to you?

Thanks,
Kajol Jain

But before going to optimizing code, Arnaldo/Jiri, is this approach looks good to you?

quoted

Pardon my ignorance, but is there no separation/whitespace between the name
and the value?

This is how we will get data via perf script

r0:0xc000000000112008
r1:0xc000000023b37920
r2:0xc00000000144c900
r3:0xc0000000bc566120
r4:0xc0000000c5600000
r5:0x2606c6506ca
r6:0xc000000023b378f8
r7:0xfffffd9f93a48f0e
.....

 And is there some significance to 10 characters for the

quoted

register name, or is that a magic number?

Most of the register name are within 10 characters, basically we are giving this
magic number to make sure we have enough space in buffer to contain all registers
name with colon.

Thanks,
Kajol Jain
 

quoted

PC

Em Tue, Jul 06, 2021 at 05:26:12PM +0530, kajoljain escreveu:

On 6/29/21 12:39 PM, kajoljain wrote:

quoted

On 6/28/21 8:19 PM, Paul A. Clarke wrote:

quoted

On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote:

quoted

Commit 48a1f565261d ("perf script python: Add more PMU fields
to event handler dict") added functionality to report fields like
weight, iregs, uregs etc via perf report.
That commit predefined buffer size to 512 bytes to print those fields.

But incase of powerpc, since we added extended regs support
in commits:

Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Commit d735599a069f ("powerpc/perf: Add extended regs support for
power10 platform")

Now iregs can carry more bytes of data and this predefined buffer size
can result to data loss in perf script output.

Patch resolve this issue by making buffer size dynamic based on number
of registers needed to print. It also changed return type for function
"regs_map" from int to void, as the return value is not being used by
the caller function "set_regs_in_dict".

Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Signed-off-by: Kajol Jain <redacted>
---
 .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 4e4aa4c97ac5..c8c9706b4643 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c

[...]

quoted

@@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict,
 			     struct evsel *evsel)
 {
 	struct perf_event_attr *attr = &evsel->core.attr;
-	char bf[512];
+
+	/*
+	 * Here value 28 is a constant size which can be used to print
+	 * one register value and its corresponds to:
+	 * 16 chars is to specify 64 bit register in hexadecimal.
+	 * 2 chars is for appending "0x" to the hexadecimal value and
+	 * 10 chars is for register name.
+	 */
+	int size = __sw_hweight64(attr->sample_regs_intr) * 28;
+	char bf[size];

I propose using a template rather than a magic number here. Something like:
const char reg_name_tmpl[] = "10 chars  ";
const char reg_value_tmpl[] = "0x0123456789abcdef";
const int size = __sw_hweight64(attr->sample_regs_intr) +
                 sizeof reg_name_tmpl + sizeof reg_value_tmpl;

Hi Paul,
   Thanks for reviewing the patch. Yes these are
some standardization we can do by creating macros for different
fields.
The basic idea is, we want to provide significant buffer size
based on number of registers present in sample_regs_intr to accommodate
all data.

Hi Arnaldo/Jiri,
   Is the approach used in this patch looks fine to you?

Yeah, and the comment you provide right above it explains it, so I think
that is enough, ok?

- Arnaldo
 

Thanks,
Kajol Jain

quoted

But before going to optimizing code, Arnaldo/Jiri, is this approach looks good to you?

quoted

Pardon my ignorance, but is there no separation/whitespace between the name
and the value?

This is how we will get data via perf script

r0:0xc000000000112008
r1:0xc000000023b37920
r2:0xc00000000144c900
r3:0xc0000000bc566120
r4:0xc0000000c5600000
r5:0x2606c6506ca
r6:0xc000000023b378f8
r7:0xfffffd9f93a48f0e
.....

 And is there some significance to 10 characters for the

quoted

register name, or is that a magic number?

Most of the register name are within 10 characters, basically we are giving this
magic number to make sure we have enough space in buffer to contain all registers
name with colon.

Thanks,
Kajol Jain
 

quoted

PC

-- 

- Arnaldo

On 7/7/21 12:45 AM, Arnaldo Carvalho de Melo wrote:

Em Tue, Jul 06, 2021 at 05:26:12PM +0530, kajoljain escreveu:

quoted

On 6/29/21 12:39 PM, kajoljain wrote:

quoted

On 6/28/21 8:19 PM, Paul A. Clarke wrote:

quoted

On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote:

quoted

Commit 48a1f565261d ("perf script python: Add more PMU fields
to event handler dict") added functionality to report fields like
weight, iregs, uregs etc via perf report.
That commit predefined buffer size to 512 bytes to print those fields.

But incase of powerpc, since we added extended regs support
in commits:

Commit 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Commit d735599a069f ("powerpc/perf: Add extended regs support for
power10 platform")

Now iregs can carry more bytes of data and this predefined buffer size
can result to data loss in perf script output.

Patch resolve this issue by making buffer size dynamic based on number
of registers needed to print. It also changed return type for function
"regs_map" from int to void, as the return value is not being used by
the caller function "set_regs_in_dict".

Fixes: 068aeea3773a ("perf powerpc: Support exposing Performance Monitor
Counter SPRs as part of extended regs")
Signed-off-by: Kajol Jain <redacted>
---
 .../util/scripting-engines/trace-event-python.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/tools/perf/util/scripting-engines/trace-event-python.c b/tools/perf/util/scripting-engines/trace-event-python.c
index 4e4aa4c97ac5..c8c9706b4643 100644
--- a/tools/perf/util/scripting-engines/trace-event-python.c
+++ b/tools/perf/util/scripting-engines/trace-event-python.c

[...]

quoted

@@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict,
 			     struct evsel *evsel)
 {
 	struct perf_event_attr *attr = &evsel->core.attr;
-	char bf[512];
+
+	/*
+	 * Here value 28 is a constant size which can be used to print
+	 * one register value and its corresponds to:
+	 * 16 chars is to specify 64 bit register in hexadecimal.
+	 * 2 chars is for appending "0x" to the hexadecimal value and
+	 * 10 chars is for register name.
+	 */
+	int size = __sw_hweight64(attr->sample_regs_intr) * 28;
+	char bf[size];

I propose using a template rather than a magic number here. Something like:
const char reg_name_tmpl[] = "10 chars  ";
const char reg_value_tmpl[] = "0x0123456789abcdef";
const int size = __sw_hweight64(attr->sample_regs_intr) +
                 sizeof reg_name_tmpl + sizeof reg_value_tmpl;

Hi Paul,
   Thanks for reviewing the patch. Yes these are
some standardization we can do by creating macros for different
fields.
The basic idea is, we want to provide significant buffer size
based on number of registers present in sample_regs_intr to accommodate
all data.

Hi Arnaldo/Jiri,
   Is the approach used in this patch looks fine to you?

Yeah, and the comment you provide right above it explains it, so I think
that is enough, ok?

Hi Arnaldo,
    Thanks for reviewing it. As you said added comment already explains
why we are taking size constant as 28, should we skip adding macros part?
Can you pull this patch.

Thanks,
Kajol Jain

- Arnaldo
 

quoted

Thanks,
Kajol Jain

quoted

But before going to optimizing code, Arnaldo/Jiri, is this approach looks good to you?

quoted

Pardon my ignorance, but is there no separation/whitespace between the name
and the value?

This is how we will get data via perf script

r0:0xc000000000112008
r1:0xc000000023b37920
r2:0xc00000000144c900
r3:0xc0000000bc566120
r4:0xc0000000c5600000
r5:0x2606c6506ca
r6:0xc000000023b378f8
r7:0xfffffd9f93a48f0e
.....

 And is there some significance to 10 characters for the

quoted

register name, or is that a magic number?

Most of the register name are within 10 characters, basically we are giving this
magic number to make sure we have enough space in buffer to contain all registers
name with colon.

Thanks,
Kajol Jain
 

quoted

PC

Em Wed, Jul 07, 2021 at 11:16:20AM +0530, kajoljain escreveu:

On 7/7/21 12:45 AM, Arnaldo Carvalho de Melo wrote:

quoted

Em Tue, Jul 06, 2021 at 05:26:12PM +0530, kajoljain escreveu:

quoted

On 6/29/21 12:39 PM, kajoljain wrote:

quoted

On 6/28/21 8:19 PM, Paul A. Clarke wrote:

quoted

On Mon, Jun 28, 2021 at 11:53:41AM +0530, Kajol Jain wrote:

quoted

@@ -713,7 +711,16 @@ static void set_regs_in_dict(PyObject *dict,
 			     struct evsel *evsel)
 {
 	struct perf_event_attr *attr = &evsel->core.attr;
-	char bf[512];
+
+	/*
+	 * Here value 28 is a constant size which can be used to print
+	 * one register value and its corresponds to:
+	 * 16 chars is to specify 64 bit register in hexadecimal.
+	 * 2 chars is for appending "0x" to the hexadecimal value and
+	 * 10 chars is for register name.
+	 */
+	int size = __sw_hweight64(attr->sample_regs_intr) * 28;
+	char bf[size];

quoted

quoted

quoted

quoted

I propose using a template rather than a magic number here. Something like:
const char reg_name_tmpl[] = "10 chars  ";
const char reg_value_tmpl[] = "0x0123456789abcdef";
const int size = __sw_hweight64(attr->sample_regs_intr) +
                 sizeof reg_name_tmpl + sizeof reg_value_tmpl;

quoted

quoted

quoted

   Thanks for reviewing the patch. Yes these are
some standardization we can do by creating macros for different
fields.
The basic idea is, we want to provide significant buffer size
based on number of registers present in sample_regs_intr to accommodate
all data.

quoted

quoted

   Is the approach used in this patch looks fine to you?

quoted

Yeah, and the comment you provide right above it explains it, so I think
that is enough, ok?

    Thanks for reviewing it. As you said added comment already explains
why we are taking size constant as 28, should we skip adding macros part?
Can you pull this patch.

Sure.

- Arnaldo