[PATCH 1/3] perf expr: Add debug logging for literals

[PATCH 1/3] perf expr: Add debug logging for literals

[Ian Rogers]

Useful for diagnosing problems with metrics.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/expr.c | 35 ++++++++++++++++++++++++-----------
 1 file changed, 24 insertions(+), 11 deletions(-)

diff --git a/tools/perf/util/expr.c b/tools/perf/util/expr.c
index 1d532b9fed29..cdbab4f959fe 100644
--- a/tools/perf/util/expr.c
+++ b/tools/perf/util/expr.c
@@ -395,12 +395,17 @@ double expr_id_data__source_count(const struct expr_id_data *data)
 double expr__get_literal(const char *literal)
 {
 	static struct cpu_topology *topology;
+	double result = NAN;
 
-	if (!strcmp("#smt_on", literal))
-		return smt_on() > 0 ? 1.0 : 0.0;
+	if (!strcmp("#smt_on", literal)) {
+		result =  smt_on() > 0 ? 1.0 : 0.0;
+		goto out;
+	}
 
-	if (!strcmp("#num_cpus", literal))
-		return cpu__max_present_cpu();
+	if (!strcmp("#num_cpus", literal)) {
+		result = cpu__max_present_cpu();
+		goto out;
+	}
 
 	/*
 	 * Assume that topology strings are consistent, such as CPUs "0-1"
@@ -415,13 +420,21 @@ double expr__get_literal(const char *literal)
 			return NAN;
 		}
 	}
-	if (!strcmp("#num_packages", literal))
-		return topology->package_cpus_lists;
-	if (!strcmp("#num_dies", literal))
-		return topology->die_cpus_lists;
-	if (!strcmp("#num_cores", literal))
-		return topology->core_cpus_lists;
+	if (!strcmp("#num_packages", literal)) {
+		result = topology->package_cpus_lists;
+		goto out;
+	}
+	if (!strcmp("#num_dies", literal)) {
+		result = topology->die_cpus_lists;
+		goto out;
+	}
+	if (!strcmp("#num_cores", literal)) {
+		result = topology->core_cpus_lists;
+		goto out;
+	}
 
 	pr_err("Unrecognized literal '%s'", literal);
-	return NAN;
+out:
+	pr_debug2("literal: %s = %f\n", literal, result);
+	return result;
 }
-- 
2.34.0.rc2.393.gf8c9666880-goog

[PATCH 2/3] perf tools: Fix SMT not detected with large core count

[Ian Rogers]

sysfs__read_int returns 0 on success, and so the fast read path was
always failing.
strtoull can only read a 64-bit bitmap. On an AMD EPYC core_cpus may look
like:
00000000,00000000,00000000,00000001,00000000,00000000,00000000,00000001
and so the sibling wasn't spotted. Fix by writing a simple hweight string
parser.

Fixes: bb629484d924 (perf tools: Simplify checking if SMT is active.)
Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/smt.c | 68 ++++++++++++++++++++++++++++++++++++-------
 1 file changed, 58 insertions(+), 10 deletions(-)

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
index 20bacd5972ad..2636be65305a 100644
--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -5,6 +5,56 @@
 #include "api/fs/fs.h"
 #include "smt.h"
 
+/**
+ * hweight_str - Returns the number of bits set in str. Stops at first non-hex
+ *	       or ',' character.
+ */
+static int hweight_str(char *str)
+{
+	int result = 0;
+
+	while (*str) {
+		switch (*str++) {
+		case '0':
+		case ',':
+			break;
+		case '1':
+		case '2':
+		case '4':
+		case '8':
+			result++;
+			break;
+		case '3':
+		case '5':
+		case '6':
+		case '9':
+		case 'a':
+		case 'A':
+		case 'c':
+		case 'C':
+			result += 2;
+			break;
+		case '7':
+		case 'b':
+		case 'B':
+		case 'd':
+		case 'D':
+		case 'e':
+		case 'E':
+			result += 3;
+			break;
+		case 'f':
+		case 'F':
+			result += 4;
+			break;
+		default:
+			goto done;
+		}
+	}
+done:
+	return result;
+}
+
 int smt_on(void)
 {
 	static bool cached;
@@ -15,9 +65,12 @@ int smt_on(void)
 	if (cached)
 		return cached_result;
 
-	if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) > 0)
-		goto done;
+	if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
+		cached = true;
+		return cached_result;
+	}
 
+	cached_result = 0;
 	ncpu = sysconf(_SC_NPROCESSORS_CONF);
 	for (cpu = 0; cpu < ncpu; cpu++) {
 		unsigned long long siblings;
@@ -35,18 +88,13 @@ int smt_on(void)
 				continue;
 		}
 		/* Entry is hex, but does not have 0x, so need custom parser */
-		siblings = strtoull(str, NULL, 16);
+		siblings = hweight_str(str);
 		free(str);
-		if (hweight64(siblings) > 1) {
+		if (siblings > 1) {
 			cached_result = 1;
-			cached = true;
 			break;
 		}
 	}
-	if (!cached) {
-		cached_result = 0;
-done:
-		cached = true;
-	}
+	cached = true;
 	return cached_result;
 }
-- 
2.34.0.rc2.393.gf8c9666880-goog

[PATCH 3/3] perf tools: Probe non-deprecated sysfs path 1st

[Ian Rogers]

Following Documentation/ABI/stable/sysfs-devices-system-cpu the
/sys/devices/system/cpu/cpuX/topology/core_cpus is deprecated in favor
of thread_siblings, so probe thread_siblings before falling back on
core_cpus.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/smt.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
index 2636be65305a..2b0a36ebf27a 100644
--- a/tools/perf/util/smt.c
+++ b/tools/perf/util/smt.c
@@ -79,11 +79,10 @@ int smt_on(void)
 		char fn[256];
 
 		snprintf(fn, sizeof fn,
-			"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
+			"devices/system/cpu/cpu%d/topology/thread_siblings", cpu);
 		if (sysfs__read_str(fn, &str, &strlen) < 0) {
 			snprintf(fn, sizeof fn,
-				"devices/system/cpu/cpu%d/topology/thread_siblings",
-				cpu);
+				"devices/system/cpu/cpu%d/topology/core_cpus", cpu);
 			if (sysfs__read_str(fn, &str, &strlen) < 0)
 				continue;
 		}
-- 
2.34.0.rc2.393.gf8c9666880-goog

Re: [PATCH 2/3] perf tools: Fix SMT not detected with large core count

[Arnaldo Carvalho de Melo]

Em Tue, Nov 23, 2021 at 02:48:20PM -0800, Ian Rogers escreveu:
> sysfs__read_int returns 0 on success, and so the fast read path was
> always failing.

Please split this into two patches, the above part should be in one, and
the strtoull in another.

Also can't we just do as ./tools/perf/util/cputopo.c and use instead
core_cpus_list?

On a 5950x:

⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu31/topology/core_cpus
80008000
⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu31/topology/core_cpus_list
15,31
⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu0/topology/core_cpus
00010001
⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu0/topology/core_cpus_list
0,16
⬢[acme@toolbox perf]$

- Arnaldo

> strtoull can only read a 64-bit bitmap. On an AMD EPYC core_cpus may look
> like:
> 00000000,00000000,00000000,00000001,00000000,00000000,00000000,00000001
> and so the sibling wasn't spotted. Fix by writing a simple hweight string
> parser.
> 
> Fixes: bb629484d924 (perf tools: Simplify checking if SMT is active.)
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/util/smt.c | 68 ++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 58 insertions(+), 10 deletions(-)
> 
> diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
> index 20bacd5972ad..2636be65305a 100644
> --- a/tools/perf/util/smt.c
> +++ b/tools/perf/util/smt.c
> @@ -5,6 +5,56 @@
>  #include "api/fs/fs.h"
>  #include "smt.h"
>  
> +/**
> + * hweight_str - Returns the number of bits set in str. Stops at first non-hex
> + *	       or ',' character.
> + */
> +static int hweight_str(char *str)
> +{
> +	int result = 0;
> +
> +	while (*str) {
> +		switch (*str++) {
> +		case '0':
> +		case ',':
> +			break;
> +		case '1':
> +		case '2':
> +		case '4':
> +		case '8':
> +			result++;
> +			break;
> +		case '3':
> +		case '5':
> +		case '6':
> +		case '9':
> +		case 'a':
> +		case 'A':
> +		case 'c':
> +		case 'C':
> +			result += 2;
> +			break;
> +		case '7':
> +		case 'b':
> +		case 'B':
> +		case 'd':
> +		case 'D':
> +		case 'e':
> +		case 'E':
> +			result += 3;
> +			break;
> +		case 'f':
> +		case 'F':
> +			result += 4;
> +			break;
> +		default:
> +			goto done;
> +		}
> +	}
> +done:
> +	return result;
> +}
> +
>  int smt_on(void)
>  {
>  	static bool cached;
> @@ -15,9 +65,12 @@ int smt_on(void)
>  	if (cached)
>  		return cached_result;
>  
> -	if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) > 0)
> -		goto done;
> +	if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
> +		cached = true;
> +		return cached_result;
> +	}
>  
> +	cached_result = 0;
>  	ncpu = sysconf(_SC_NPROCESSORS_CONF);
>  	for (cpu = 0; cpu < ncpu; cpu++) {
>  		unsigned long long siblings;
> @@ -35,18 +88,13 @@ int smt_on(void)
>  				continue;
>  		}
>  		/* Entry is hex, but does not have 0x, so need custom parser */
> -		siblings = strtoull(str, NULL, 16);
> +		siblings = hweight_str(str);
>  		free(str);
> -		if (hweight64(siblings) > 1) {
> +		if (siblings > 1) {
>  			cached_result = 1;
> -			cached = true;
>  			break;
>  		}
>  	}
> -	if (!cached) {
> -		cached_result = 0;
> -done:
> -		cached = true;
> -	}
> +	cached = true;
>  	return cached_result;
>  }
> -- 
> 2.34.0.rc2.393.gf8c9666880-goog

-- 

- Arnaldo

Re: [PATCH 2/3] perf tools: Fix SMT not detected with large core count

[Ian Rogers]

On Tue, Nov 23, 2021 at 3:34 PM Arnaldo Carvalho de Melo
<acme@kernel.org> wrote:
>
> Em Tue, Nov 23, 2021 at 02:48:20PM -0800, Ian Rogers escreveu:
> > sysfs__read_int returns 0 on success, and so the fast read path was
> > always failing.
>
> Please split this into two patches, the above part should be in one, and
> the strtoull in another.

Will do.

> Also can't we just do as ./tools/perf/util/cputopo.c and use instead
> core_cpus_list?

It is more complex for the list case as the list may have a range. It
shouldn't really matter with the active fix in any case. I think
ideally we'd have an abstraction like cpuset in util-linux:
https://github.com/util-linux/util-linux/blob/master/lib/cpuset.c
This is a bit beyond what I'm trying to fix here.

Thanks,
Ian

> On a 5950x:
>
> ⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu31/topology/core_cpus
> 80008000
> ⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu31/topology/core_cpus_list
> 15,31
> ⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu0/topology/core_cpus
> 00010001
> ⬢[acme@toolbox perf]$ cat /sys/devices/system/cpu/cpu0/topology/core_cpus_list
> 0,16
> ⬢[acme@toolbox perf]$
>
> - Arnaldo
>
> > strtoull can only read a 64-bit bitmap. On an AMD EPYC core_cpus may look
> > like:
> > 00000000,00000000,00000000,00000001,00000000,00000000,00000000,00000001
> > and so the sibling wasn't spotted. Fix by writing a simple hweight string
> > parser.
> >
> > Fixes: bb629484d924 (perf tools: Simplify checking if SMT is active.)
> > Signed-off-by: Ian Rogers <irogers@google.com>
> > ---
> >  tools/perf/util/smt.c | 68 ++++++++++++++++++++++++++++++++++++-------
> >  1 file changed, 58 insertions(+), 10 deletions(-)
> >
> > diff --git a/tools/perf/util/smt.c b/tools/perf/util/smt.c
> > index 20bacd5972ad..2636be65305a 100644
> > --- a/tools/perf/util/smt.c
> > +++ b/tools/perf/util/smt.c
> > @@ -5,6 +5,56 @@
> >  #include "api/fs/fs.h"
> >  #include "smt.h"
> >
> > +/**
> > + * hweight_str - Returns the number of bits set in str. Stops at first non-hex
> > + *          or ',' character.
> > + */
> > +static int hweight_str(char *str)
> > +{
> > +     int result = 0;
> > +
> > +     while (*str) {
> > +             switch (*str++) {
> > +             case '0':
> > +             case ',':
> > +                     break;
> > +             case '1':
> > +             case '2':
> > +             case '4':
> > +             case '8':
> > +                     result++;
> > +                     break;
> > +             case '3':
> > +             case '5':
> > +             case '6':
> > +             case '9':
> > +             case 'a':
> > +             case 'A':
> > +             case 'c':
> > +             case 'C':
> > +                     result += 2;
> > +                     break;
> > +             case '7':
> > +             case 'b':
> > +             case 'B':
> > +             case 'd':
> > +             case 'D':
> > +             case 'e':
> > +             case 'E':
> > +                     result += 3;
> > +                     break;
> > +             case 'f':
> > +             case 'F':
> > +                     result += 4;
> > +                     break;
> > +             default:
> > +                     goto done;
> > +             }
> > +     }
> > +done:
> > +     return result;
> > +}
> > +
> >  int smt_on(void)
> >  {
> >       static bool cached;
> > @@ -15,9 +65,12 @@ int smt_on(void)
> >       if (cached)
> >               return cached_result;
> >
> > -     if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) > 0)
> > -             goto done;
> > +     if (sysfs__read_int("devices/system/cpu/smt/active", &cached_result) >= 0) {
> > +             cached = true;
> > +             return cached_result;
> > +     }
> >
> > +     cached_result = 0;
> >       ncpu = sysconf(_SC_NPROCESSORS_CONF);
> >       for (cpu = 0; cpu < ncpu; cpu++) {
> >               unsigned long long siblings;
> > @@ -35,18 +88,13 @@ int smt_on(void)
> >                               continue;
> >               }
> >               /* Entry is hex, but does not have 0x, so need custom parser */
> > -             siblings = strtoull(str, NULL, 16);
> > +             siblings = hweight_str(str);
> >               free(str);
> > -             if (hweight64(siblings) > 1) {
> > +             if (siblings > 1) {
> >                       cached_result = 1;
> > -                     cached = true;
> >                       break;
> >               }
> >       }
> > -     if (!cached) {
> > -             cached_result = 0;
> > -done:
> > -             cached = true;
> > -     }
> > +     cached = true;
> >       return cached_result;
> >  }
> > --
> > 2.34.0.rc2.393.gf8c9666880-goog
>
> --
>
> - Arnaldo