[PATCH v1] perf test: Allow tolerance for leader sampling test

[PATCH v1] 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 | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
index ba8d873d3ca7..1bbe16fb3420 100755
--- a/tools/perf/tests/shell/record.sh
+++ b/tools/perf/tests/shell/record.sh
@@ -238,22 +238,35 @@ 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 < $script_output
-  echo "Basic leader sampling test [Success]"
+  if [[ "$(echo "scale=2; $invalid_counts/($invalid_counts+$valid_counts)" | bc)" > 1-$tolerance_rate ]]
+  then
+      echo "Leader sampling [Failed inconsistent cycles count]"
+      err=1
+  else
+    echo "Basic leader sampling test [Success]"
+  fi
 }

 test_topdown_leader_sampling() {
--
2.49.0.472.ge94155a9ec-goog

Re: [PATCH v1] perf test: Allow tolerance for leader sampling test

[Ian Rogers]

On Tue, Apr 1, 2025 at 10:23 AM 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>

Reviewed-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
>  tools/perf/tests/shell/record.sh | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
> index ba8d873d3ca7..1bbe16fb3420 100755
> --- a/tools/perf/tests/shell/record.sh
> +++ b/tools/perf/tests/shell/record.sh
> @@ -238,22 +238,35 @@ 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 < $script_output
> -  echo "Basic leader sampling test [Success]"
> +  if [[ "$(echo "scale=2; $invalid_counts/($invalid_counts+$valid_counts)" | bc)" > 1-$tolerance_rate ]]
> +  then
> +      echo "Leader sampling [Failed inconsistent cycles count]"
> +      err=1
> +  else
> +    echo "Basic leader sampling test [Success]"
> +  fi
>  }
>
>  test_topdown_leader_sampling() {
> --
> 2.49.0.472.ge94155a9ec-goog
>

Re: [PATCH v1] perf test: Allow tolerance for leader sampling test

[Namhyung Kim]

Hello,

On Tue, Apr 01, 2025 at 10:22:39AM -0700, Chun-Tse Shao 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 | 25 +++++++++++++++++++------
>  1 file changed, 19 insertions(+), 6 deletions(-)
> 
> diff --git a/tools/perf/tests/shell/record.sh b/tools/perf/tests/shell/record.sh
> index ba8d873d3ca7..1bbe16fb3420 100755
> --- a/tools/perf/tests/shell/record.sh
> +++ b/tools/perf/tests/shell/record.sh
> @@ -238,22 +238,35 @@ 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 < $script_output
> -  echo "Basic leader sampling test [Success]"
> +  if [[ "$(echo "scale=2; $invalid_counts/($invalid_counts+$valid_counts)" | bc)" > 1-$tolerance_rate ]]

Shouldn't it be double parenthesis to use numeric comparisons?
Also I'm not sure if bash supports floating-point arithmetic.
It'd be better to compare the value in bc and use its return value.

Thanks,
Namhyung


> +  then
> +      echo "Leader sampling [Failed inconsistent cycles count]"
> +      err=1
> +  else
> +    echo "Basic leader sampling test [Success]"
> +  fi
>  }
> 
>  test_topdown_leader_sampling() {
> --
> 2.49.0.472.ge94155a9ec-goog
>