[PATCH] perf, tools: Add PERF_PID

[PATCH] perf, tools: Add PERF_PID

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

It's currently difficult to filter out perf itself using a filter.
This can give cascading effects during IO tracing when the IO
perf does itself causes more trace output.

The best way to filter is to use the pid. But it's difficult to get the pid
of perf without using hacks.

Add a PERF_PID meta variable to the perf filter that contains the current pid.

With this patch the following works

% perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...

This won't work for more complex perf pipe lines with multiple processes,
but at least solves the problem nicely for a single perf.

v2: Remove debug code. Don't use zero padding (Namhyung)
v3: Correct patch.
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-record.txt | 2 +-
 tools/perf/util/parse-events.c           | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d460049..b6c5e51 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -41,7 +41,7 @@ OPTIONS
           'mem:0x1000:rw'.
 
 --filter=<filter>::
-        Event filter.
+        Event filter. PERF_PID represents the perf pid.
 
 -a::
 --all-cpus::
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 1e15df1..def8651 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -967,6 +967,7 @@ int parse_filter(const struct option *opt, const char *str,
 {
 	struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
 	struct perf_evsel *last = NULL;
+	char *pid;
 
 	if (evlist->nr_entries > 0)
 		last = perf_evlist__last(evlist);
@@ -983,6 +984,13 @@ int parse_filter(const struct option *opt, const char *str,
 		return -1;
 	}
 
+	/* Assume a pid has not more than 8 characters */
+	pid = strstr(last->filter, "PERF_PID");
+	if (pid) {
+		char buf[9];
+		snprintf(buf, 9, "%8d", getpid());
+		memcpy(pid, buf, 8);
+	}
 	return 0;
 }
 
-- 
1.9.3

Re: [PATCH] perf, tools: Add PERF_PID

[Brendan Gregg]

On Tue, Sep 9, 2014 at 5:03 PM, Andi Kleen <andi@firstfloor.org> wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> It's currently difficult to filter out perf itself using a filter.
> This can give cascading effects during IO tracing when the IO
> perf does itself causes more trace output.
>
> The best way to filter is to use the pid. But it's difficult to get the pid
> of perf without using hacks.
>
> Add a PERF_PID meta variable to the perf filter that contains the current pid.
>
> With this patch the following works
>
> % perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...
>
> This won't work for more complex perf pipe lines with multiple processes,
> but at least solves the problem nicely for a single perf.

Thank you, this will be handy. I tested it and it works.

It will mean I can avoid hacks like this:
https://github.com/brendangregg/perf-tools/blob/d30e8a1a9f136d532ba78c6d48aedb99dc316be9/syscount#L144

I think it's unrelated to this patch, but the very next test I tried
didn't work as expected:

# perf record -e 'syscalls:sys_enter_*' --filter 'common_pid !=
PERF_PID' -a sleep 5

It only filters the last event from the wildcard expansion, leaving
write() unfiltered. Looks like it's because parse_filter() is only
setting the filter for perf_evlist__last(), instead of doing an
evlist__for_each(). How best to deal with this can be addressed in a
separate patch later.

Brendan

Re: [PATCH] perf, tools: Add PERF_PID

[Arnaldo Carvalho de Melo]

Em Tue, Sep 09, 2014 at 05:03:53PM -0700, Andi Kleen escreveu:
> From: Andi Kleen <ak@linux.intel.com>
> 
> It's currently difficult to filter out perf itself using a filter.
> This can give cascading effects during IO tracing when the IO
> perf does itself causes more trace output.
> 
> The best way to filter is to use the pid. But it's difficult to get the pid
> of perf without using hacks.
> 
> Add a PERF_PID meta variable to the perf filter that contains the current pid.
> 
> With this patch the following works
> 
> % perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...
> 
> This won't work for more complex perf pipe lines with multiple processes,
> but at least solves the problem nicely for a single perf.
 
> @@ -983,6 +984,13 @@ int parse_filter(const struct option *opt, const char *str,
>  		return -1;
>  	}
>  
> +	/* Assume a pid has not more than 8 characters */

> +	pid = strstr(last->filter, "PERF_PID");
> +	if (pid) {
> +		char buf[9];
> +		snprintf(buf, 9, "%8d", getpid());
> +		memcpy(pid, buf, 8);

Can we please remove this assumption?

If the get to be more than 8 chars we'll be just truncating stuff and
possibly filtering some other, unrelated process, no?

       pid_t getpid(void);

typedef __pid_t pid_t;
__STD_TYPE __PID_T_TYPE __pid_t;	/* Type of process identifications.  */
/usr/include/bits/typesizes.h:#define __PID_T_TYPE __S32_TYPE
/usr/include/bits/types.h:#define	__S32_TYPE		int
[acme@zoo linux]$ uname -a
Linux zoo.ghostprotocols.net 3.17.0-rc1+ #2 SMP Thu Aug 21 12:25:42 BRT 2014 x86_64 x86_64 x86_64 GNU/Linux

[acme@zoo ~]$ cat a.c
#include <limits.h>
#include <stdio.h>

int main(int argc, char *argv[])
{
	printf("%8d", INT_MAX);
}
[acme@zoo ~]$ make a
cc     a.c   -o a
[acme@zoo ~]$ ./a | wc -c
10
[acme@zoo ~]$

The feature is needed, no doubt about it, thanks for working on it.

I guess we need the equivalent of (python regexp) s/PERF_PID/("%d" % getpid())/g
to properly implement this.

- Arnaldo

[PATCH] perf, tools: Add PERF_PID

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

It's currently difficult to filter out perf itself using a filter.
This can give cascading effects during IO tracing when the IO
perf does itself causes more trace output.

The best way to filter is to use the pid. But it's difficult to get the pid
of perf without using hacks.

Add a PERF_PID meta variable to the perf filter that contains the current pid.

With this patch the following works

% perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...

This won't work for more complex perf pipe lines with multiple processes,
but at least solves the problem nicely for a single perf.

v2: Remove debug code. Don't use zero padding (Namhyung)
v3: Correct patch.
v4: Handle arbitary pid length.
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-record.txt |  2 +-
 tools/perf/util/parse-events.c           | 20 +++++++++++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d460049..b6c5e51 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -41,7 +41,7 @@ OPTIONS
           'mem:0x1000:rw'.
 
 --filter=<filter>::
-        Event filter.
+        Event filter. PERF_PID represents the perf pid.
 
 -a::
 --all-cpus::
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 1e15df1..f974941 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -967,6 +967,8 @@ int parse_filter(const struct option *opt, const char *str,
 {
 	struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
 	struct perf_evsel *last = NULL;
+	char *pid, buf[30], *p, *o;
+	int len, plen;
 
 	if (evlist->nr_entries > 0)
 		last = perf_evlist__last(evlist);
@@ -977,12 +979,28 @@ int parse_filter(const struct option *opt, const char *str,
 		return -1;
 	}
 
-	last->filter = strdup(str);
+	plen = sprintf(buf, "%d", getpid());
+	len = strlen(str) + 1;
+	for (pid = strstr(str, "PERF_PID"); pid;
+	     pid = strstr(pid + 1, "PERF_PID")) {
+		len += plen - 8;
+	}
+
+	last->filter = malloc(len);
 	if (last->filter == NULL) {
 		fprintf(stderr, "not enough memory to hold filter string\n");
 		return -1;
 	}
 
+	o = last->filter;
+	for (p = str; *p; ) {
+		if (*p == 'P' && !strncmp(p, "PERF_PID", 8)) {
+			strcpy(o, buf);
+			o += plen;
+			p += sizeof("PERF_PID") - 1;
+		} else
+			*o++ = *p++;
+	}
 	return 0;
 }
 
-- 
1.9.3

[PATCH] perf, tools: Add PERF_PID

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

It's currently difficult to filter out perf itself using a filter.
This can give cascading effects during IO tracing when the IO
perf does itself causes more trace output.

The best way to filter is to use the pid. But it's difficult to get the pid
of perf without using hacks.

Add a PERF_PID meta variable to the perf filter that contains the current pid.

With this patch the following works

% perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...

This won't work for more complex perf pipe lines with multiple processes,
but at least solves the problem nicely for a single perf.

v2: Remove debug code. Don't use zero padding (Namhyung)
v3: Correct patch.
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-record.txt | 2 +-
 tools/perf/util/parse-events.c           | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d460049..b6c5e51 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -41,7 +41,7 @@ OPTIONS
           'mem:0x1000:rw'.
 
 --filter=<filter>::
-        Event filter.
+        Event filter. PERF_PID represents the perf pid.
 
 -a::
 --all-cpus::
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 1e15df1..def8651 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -967,6 +967,7 @@ int parse_filter(const struct option *opt, const char *str,
 {
 	struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
 	struct perf_evsel *last = NULL;
+	char *pid;
 
 	if (evlist->nr_entries > 0)
 		last = perf_evlist__last(evlist);
@@ -983,6 +984,13 @@ int parse_filter(const struct option *opt, const char *str,
 		return -1;
 	}
 
+	/* Assume a pid has not more than 8 characters */
+	pid = strstr(last->filter, "PERF_PID");
+	if (pid) {
+		char buf[9];
+		snprintf(buf, 9, "%8d", getpid());
+		memcpy(pid, buf, 8);
+	}
 	return 0;
 }
 
-- 
1.9.3

Re: [PATCH] perf, tools: Add PERF_PID

[Andi Kleen]

On Tue, Aug 19, 2014 at 05:02:22AM -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>

Please disregard. I posted the wrong patch.

-Andi

[PATCH] perf, tools: Add PERF_PID

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

It's currently difficult to filter out perf itself using a filter.
This can give cascading effects during IO tracing when the IO
perf does itself causes more trace output.

The best way to filter is to use the pid. But it's difficult to get the pid
of perf without using hacks.

Add a PERF_PID meta variable to the perf filter that contains the current pid.

With this patch the following works

% perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...

This won't work for more complex perf pipe lines with multiple processes,
but at least solves the problem nicely for a single perf.

v2: Remove debug code. Don't use zero padding (Namhyung)
Acked-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-record.txt | 2 +-
 tools/perf/util/parse-events.c           | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d460049..b6c5e51 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -41,7 +41,7 @@ OPTIONS
           'mem:0x1000:rw'.
 
 --filter=<filter>::
-        Event filter.
+        Event filter. PERF_PID represents the perf pid.
 
 -a::
 --all-cpus::
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 1e15df1..90ed63f 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -967,6 +967,7 @@ int parse_filter(const struct option *opt, const char *str,
 {
 	struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
 	struct perf_evsel *last = NULL;
+	char *pid;
 
 	if (evlist->nr_entries > 0)
 		last = perf_evlist__last(evlist);
@@ -983,6 +984,14 @@ int parse_filter(const struct option *opt, const char *str,
 		return -1;
 	}
 
+	/* Assume a pid has not more than 8 characters */
+	pid = strstr(last->filter, "PERF_PID");
+	if (pid) {
+		char buf[9];
+		snprintf(buf, 9, "%08d", getpid());
+		memcpy(pid, buf, 8);
+	}
+	fprintf(stderr, "filter |%s|\n", last->filter);
 	return 0;
 }
 
-- 
1.9.3

Re: [PATCH] perf, tools: Add PERF_PID

[Namhyung Kim]

Hi Andi,

On Wed, 13 Aug 2014 14:12:17 -0700, Andi Kleen wrote:
> From: Andi Kleen <ak@linux.intel.com>
>
> It's currently difficult to filter out perf itself using a filter.
> This can give cascading effects during IO tracing when the IO
> perf does itself causes more trace output.
>
> The best way to filter is to use the pid. But it's difficult to get the pid
> of perf without using hacks.
>
> Add a PERF_PID meta variable to the perf filter that contains the current pid.
>
> With this patch the following works
>
> % perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...
>
> This won't work for more complex perf pipe lines with multiple processes,
> but at least solves the problem nicely for a single perf.
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>

I like the idea, so with comments below fixed:

Acked-by: Namhyung Kim <namhyung@kernel.org>

Thanks,
Namhyung


[SNIP]
> +	/* Assume a pid has not more than 8 characters */
> +	pid = strstr(last->filter, "PERF_PID");
> +	if (pid) {
> +		char buf[9];
> +		snprintf(buf, 9, "%08d", getpid());

Why do you add zero-paddings?  I guess it'd confuse the parser as if
it's an octal digits.  What about just using "%8d"?  It seems the parser
ignores whitespaces between tokens..


> +		memcpy(pid, buf, 8);
> +	}
> +	fprintf(stderr, "filter |%s|\n", last->filter);

Isn't it a debug message?

Thanks,
Namhyung


>  	return 0;
>  }

[PATCH] perf, tools: Add PERF_PID

[Andi Kleen]

From: Andi Kleen <ak@linux.intel.com>

It's currently difficult to filter out perf itself using a filter.
This can give cascading effects during IO tracing when the IO
perf does itself causes more trace output.

The best way to filter is to use the pid. But it's difficult to get the pid
of perf without using hacks.

Add a PERF_PID meta variable to the perf filter that contains the current pid.

With this patch the following works

% perf record -e syscalls:sys_enter_write -a --filter 'common_pid != PERF_PID' ...

This won't work for more complex perf pipe lines with multiple processes,
but at least solves the problem nicely for a single perf.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
 tools/perf/Documentation/perf-record.txt | 2 +-
 tools/perf/util/parse-events.c           | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d460049..b6c5e51 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -41,7 +41,7 @@ OPTIONS
           'mem:0x1000:rw'.
 
 --filter=<filter>::
-        Event filter.
+        Event filter. PERF_PID represents the perf pid.
 
 -a::
 --all-cpus::
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index 1e15df1..90ed63f 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -967,6 +967,7 @@ int parse_filter(const struct option *opt, const char *str,
 {
 	struct perf_evlist *evlist = *(struct perf_evlist **)opt->value;
 	struct perf_evsel *last = NULL;
+	char *pid;
 
 	if (evlist->nr_entries > 0)
 		last = perf_evlist__last(evlist);
@@ -983,6 +984,14 @@ int parse_filter(const struct option *opt, const char *str,
 		return -1;
 	}
 
+	/* Assume a pid has not more than 8 characters */
+	pid = strstr(last->filter, "PERF_PID");
+	if (pid) {
+		char buf[9];
+		snprintf(buf, 9, "%08d", getpid());
+		memcpy(pid, buf, 8);
+	}
+	fprintf(stderr, "filter |%s|\n", last->filter);
 	return 0;
 }
 
-- 
1.9.3