[PATCH v2] perf test: Allow tolerance for leader sampling test

[PATCH v2] perf test: Allow tolerance for leader sampling test

[Thomas Richter]

V2: Changed bc invocation to return 0 on success and 1 on error.

There is a known issue that the leader sampling is inconsistent, since
throttle only affect leader, not the slave. The detail is in [1]. To
maintain test coverage, this patch sets a tolerance rate of 80% to
accommodate the throttled samples and prevent test failures due to
throttling.

[1] lore.kernel.org/20250328182752.769662-1-ctshao@google.com

Signed-off-by: Chun-Tse Shao <ctshao@google.com>
Suggested-by: Ian Rogers <irogers@google.com>
Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/shell/record.sh | 26 ++++++++++++++++++++------
 1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
index ba8d873d3ca7..b17e8b0680e2 100755
--- a/tools/perf/tests/shell/record.sh
+++ b/tools/perf/tests/shell/record.sh
@@ -238,22 +238,36 @@ test_leader_sampling() {
     err=1
     return
   fi
+  perf script -i "${perfdata}" | grep brstack > $script_output
+  # Check if the two instruction counts are equal in each record.
+  # However, the throttling code doesn't consider event grouping. During throttling, only the
+  # leader is stopped, causing the slave's counts significantly higher. To temporarily solve this,
+  # let's set the tolerance rate to 80%.
+  # TODO: Revert the code for tolerance once the throttling mechanism is fixed.
   index=0
-  perf script -i "${perfdata}" > $script_output
+  valid_counts=0
+  invalid_counts=0
+  tolerance_rate=0.8
   while IFS= read -r line
   do
-    # Check if the two instruction counts are equal in each record
     cycles=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="cycles:") print $(i-1)}')
     if [ $(($index%2)) -ne 0 ] && [ ${cycles}x != ${prev_cycles}x ]
     then
-      echo "Leader sampling [Failed inconsistent cycles count]"
-      err=1
-      return
+      invalid_counts=$(($invalid_counts+1))
+    else
+      valid_counts=$(($valid_counts+1))
     fi
     index=$(($index+1))
     prev_cycles=$cycles
   done < $script_output
-  echo "Basic leader sampling test [Success]"
+  isok=$(echo "scale=2; val=$invalid_counts/($invalid_counts+$valid_counts); if (val < (1-$tolerance_rate)) { 0 } else { 1 };" | bc -q)
+  if [ $isok -eq 1 ]
+  then
+     echo "Leader sampling [Failed inconsistent cycles count]"
+     err=1
+  else
+    echo "Basic leader sampling test [Success]"
+  fi
 }
 
 test_topdown_leader_sampling() {
-- 
2.49.0

[PATCH v2] perf test: Allow tolerance for leader sampling test

[Chun-Tse Shao]

There is a known issue that the leader sampling is inconsistent, since
throttle only affect leader, not the slave. The detail is in [1]. To
maintain test coverage, this patch sets a tolerance rate of 80% to
accommodate the throttled samples and prevent test failures due to
throttling.

[1] lore.kernel.org/20250328182752.769662-1-ctshao@google.com

Signed-off-by: Chun-Tse Shao <ctshao@google.com>
Suggested-by: Ian Rogers <irogers@google.com>
Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
---
 tools/perf/tests/shell/record.sh | 28 ++++++++++++++++++++++++----
 1 file changed, 24 insertions(+), 4 deletions(-)

diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
index ba8d873d3ca7..06a718e80121 100755
--- a/tools/perf/tests/shell/record.sh
+++ b/tools/perf/tests/shell/record.sh
@@ -240,19 +240,39 @@ test_leader_sampling() {
   fi
   index=0
   perf script -i "${perfdata}" > $script_output
+  # Check if the two instruction counts are equal in each record.
+  # However, the throttling code doesn't consider event grouping. During throttling, only the
+  # leader is stopped, causing the slave's counts significantly higher. To temporarily solve this,
+  # let's set the tolerance rate to 80%.
+  # TODO: Revert the code for tolerance once the throttling mechanism is fixed.
+  valid_counts=0
+  invalid_counts=0
+  tolerance_rate=0.8
   while IFS= read -r line
   do
-    # Check if the two instruction counts are equal in each record
     cycles=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="cycles:") print $(i-1)}')
     if [ $(($index%2)) -ne 0 ] && [ ${cycles}x != ${prev_cycles}x ]
     then
-      echo "Leader sampling [Failed inconsistent cycles count]"
-      err=1
-      return
+      invalid_counts=$(($invalid_counts+1))
+    else
+      valid_counts=$(($valid_counts+1))
     fi
     index=$(($index+1))
     prev_cycles=$cycles
   done < $script_output
+  total_counts=$(bc <<< "$invalid_counts+$valid_counts")
+  if (( $(bc <<< "$total_counts <= 0") ))
+  then
+      echo "Leader sampling [No sample generated]"
+      err=1
+      return
+  fi
+  if (( $(bc <<< "scale=3; $invalid_counts/$total_counts > 1-$tolerance_rate") ))
+  then
+      echo "Leader sampling [Failed inconsistent cycles count]"
+      err=1
+      return
+  fi
   echo "Basic leader sampling test [Success]"
 }

--
2.49.0.504.g3bcea36a83-goog

Re: [PATCH v2] perf test: Allow tolerance for leader sampling test

[Chun-Tse Shao]

Please ignore this since Thomas Richter already submitted the fix [1]
with bc invocation.

[1] lore.kernel.org/20250408074641.1471473-1-tmricht@linux.ibm.com/

Thanks,
CT

On Wed, Apr 9, 2025 at 4:12 PM Chun-Tse Shao <ctshao@google.com> wrote:
>
> There is a known issue that the leader sampling is inconsistent, since
> throttle only affect leader, not the slave. The detail is in [1]. To
> maintain test coverage, this patch sets a tolerance rate of 80% to
> accommodate the throttled samples and prevent test failures due to
> throttling.
>
> [1] lore.kernel.org/20250328182752.769662-1-ctshao@google.com
>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> Suggested-by: Ian Rogers <irogers@google.com>
> Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
> Tested-by: Thomas Richter <tmricht@linux.ibm.com>
> ---
>  tools/perf/tests/shell/record.sh | 28 ++++++++++++++++++++++++----
>  1 file changed, 24 insertions(+), 4 deletions(-)
>
> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
> index ba8d873d3ca7..06a718e80121 100755
> --- a/tools/perf/tests/shell/record.sh
> +++ b/tools/perf/tests/shell/record.sh
> @@ -240,19 +240,39 @@ test_leader_sampling() {
>    fi
>    index=0
>    perf script -i "${perfdata}" > $script_output
> +  # Check if the two instruction counts are equal in each record.
> +  # However, the throttling code doesn't consider event grouping. During throttling, only the
> +  # leader is stopped, causing the slave's counts significantly higher. To temporarily solve this,
> +  # let's set the tolerance rate to 80%.
> +  # TODO: Revert the code for tolerance once the throttling mechanism is fixed.
> +  valid_counts=0
> +  invalid_counts=0
> +  tolerance_rate=0.8
>    while IFS= read -r line
>    do
> -    # Check if the two instruction counts are equal in each record
>      cycles=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="cycles:") print $(i-1)}')
>      if [ $(($index%2)) -ne 0 ] && [ ${cycles}x != ${prev_cycles}x ]
>      then
> -      echo "Leader sampling [Failed inconsistent cycles count]"
> -      err=1
> -      return
> +      invalid_counts=$(($invalid_counts+1))
> +    else
> +      valid_counts=$(($valid_counts+1))
>      fi
>      index=$(($index+1))
>      prev_cycles=$cycles
>    done < $script_output
> +  total_counts=$(bc <<< "$invalid_counts+$valid_counts")
> +  if (( $(bc <<< "$total_counts <= 0") ))
> +  then
> +      echo "Leader sampling [No sample generated]"
> +      err=1
> +      return
> +  fi
> +  if (( $(bc <<< "scale=3; $invalid_counts/$total_counts > 1-$tolerance_rate") ))
> +  then
> +      echo "Leader sampling [Failed inconsistent cycles count]"
> +      err=1
> +      return
> +  fi
>    echo "Basic leader sampling test [Success]"
>  }
>
> --
> 2.49.0.504.g3bcea36a83-goog
>

Re: [PATCH v2] perf test: Allow tolerance for leader sampling test

[Chun-Tse Shao]

On Tue, Apr 08, 2025 at 09:46:41AM +0200, Thomas Richter wrote:
> V2: Changed bc invocation to return 0 on success and 1 on error.
>
> There is a known issue that the leader sampling is inconsistent, since
> throttle only affect leader, not the slave. The detail is in [1]. To
> maintain test coverage, this patch sets a tolerance rate of 80% to
> accommodate the throttled samples and prevent test failures due to
> throttling.
>
> [1] lore.kernel.org/20250328182752.769662-1-ctshao@google.com
>
> Signed-off-by: Chun-Tse Shao <ctshao@google.com>
> Suggested-by: Ian Rogers <irogers@google.com>
> Suggested-by: Thomas Richter <tmricht@linux.ibm.com>
> Tested-by: Thomas Richter <tmricht@linux.ibm.com>
> Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
> ---
>  tools/perf/tests/shell/record.sh | 26 ++++++++++++++++++++------
>  1 file changed, 20 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
> index ba8d873d3ca7..b17e8b0680e2 100755
> --- a/tools/perf/tests/shell/record.sh
> +++ b/tools/perf/tests/shell/record.sh
> @@ -238,22 +238,36 @@ test_leader_sampling() {
>      err=1
>      return
>    fi
> +  perf script -i "${perfdata}" | grep brstack > $script_output
> +  # Check if the two instruction counts are equal in each record.
> +  # However, the throttling code doesn't consider event grouping. During throttling, only the
> +  # leader is stopped, causing the slave's counts significantly higher. To temporarily solve this,
> +  # let's set the tolerance rate to 80%.
> +  # TODO: Revert the code for tolerance once the throttling mechanism is fixed.
>    index=0
> -  perf script -i "${perfdata}" > $script_output
> +  valid_counts=0
> +  invalid_counts=0
> +  tolerance_rate=0.8
>    while IFS= read -r line
>    do
> -    # Check if the two instruction counts are equal in each record
>      cycles=$(echo $line | awk '{for(i=1;i<=NF;i++) if($i=="cycles:") print $(i-1)}')
>      if [ $(($index%2)) -ne 0 ] && [ ${cycles}x != ${prev_cycles}x ]
>      then
> -      echo "Leader sampling [Failed inconsistent cycles count]"
> -      err=1
> -      return
> +      invalid_counts=$(($invalid_counts+1))
> +    else
> +      valid_counts=$(($valid_counts+1))
>      fi
>      index=$(($index+1))
>      prev_cycles=$cycles
>    done < $script_output
> -  echo "Basic leader sampling test [Success]"

Would you like to add an simple division by 0 check?

  total_counts=$(bc <<< "$invalid_counts+$valid_counts")
  if (( $(bc <<< "$total_counts <= 0") ))
  then
    echo "Leader sampling [No sample generated]"
    err=1
    return
  fi

And then `$invalid_counts+$valid_counts` can be replaced by
$total_counts

Thanks,
CT

> +  isok=$(echo "scale=2; val=$invalid_counts/($invalid_counts+$valid_counts); if (val < (1-$tolerance_rate)) { 0 } else { 1 };" | bc -q)
> +  if [ $isok -eq 1 ]
> +  then
> +     echo "Leader sampling [Failed inconsistent cycles count]"
> +     err=1
> +  else
> +    echo "Basic leader sampling test [Success]"
> +  fi
>  }
>
>  test_topdown_leader_sampling() {
> --
> 2.49.0
>