[libcxx-commits] [libcxx] bf2fc12 - [libc++] Skip dry-runs of the workflow in dispatch-benchmarks (#215637)

[via libcxx-commits]

Author: Louis Dionne
Date: 2026-08-11T14:59:28-04:00
New Revision: bf2fc124673798d92c70d368652ad30769dbff80

URL: https://github.com/llvm/llvm-project/commit/bf2fc124673798d92c70d368652ad30769dbff80
DIFF: https://github.com/llvm/llvm-project/commit/bf2fc124673798d92c70d368652ad30769dbff80.diff

LOG: [libc++] Skip dry-runs of the workflow in dispatch-benchmarks (#215637)

When submitting a dry-run of the commit-benchmarking workflow, don't
count it towards the limits for re-runs in dispatch-benchmarks.

Added: 
    

Modified: 
    .github/workflows/libcxx-benchmark-commit.yml
    libcxx/utils/ci/lnt/dispatch-benchmarks

Removed: 
    


################################################################################
diff  --git a/.github/workflows/libcxx-benchmark-commit.yml b/.github/workflows/libcxx-benchmark-commit.yml
index c8c7f03104fc2..66dcd60008806 100644
--- a/.github/workflows/libcxx-benchmark-commit.yml
+++ b/.github/workflows/libcxx-benchmark-commit.yml
@@ -5,7 +5,7 @@
 name: "[libc++] Run benchmark suite against commit"
 
 # Keep in sync with libcxx/utils/ci/lnt/dispatch-benchmarks
-run-name: "[libc++] Run benchmark suite against ${{ inputs.commit }} on ${{ inputs.lnt-machine }}"
+run-name: "[libc++] Run benchmark suite against ${{ inputs.commit }} on ${{ inputs.lnt-machine }}${{ !inputs.submit-lnt && ' (dry run)' || '' }}"
 
 permissions:
   contents: read

diff  --git a/libcxx/utils/ci/lnt/dispatch-benchmarks b/libcxx/utils/ci/lnt/dispatch-benchmarks
index 45a343cafe64c..b022008799ad4 100755
--- a/libcxx/utils/ci/lnt/dispatch-benchmarks
+++ b/libcxx/utils/ci/lnt/dispatch-benchmarks
@@ -7,7 +7,7 @@
 #
 # ===----------------------------------------------------------------------===##
 
-from typing import Dict, List, NamedTuple, Optional, Sequence, TextIO
+from typing import Dict, List, NamedTuple, Optional, Sequence, Set, TextIO
 import argparse
 import common
 import github
@@ -20,6 +20,12 @@ import sys
 import tabulate
 
 
+class RunName(NamedTuple):
+    """The name of a workflow run and the information it encodes."""
+    target: common.Target
+    dry_run: bool # whether that workflow run was only a dry-run
+
+
 class WorkflowRun(NamedTuple):
     """A run of the benchmark workflow, as the Github API describes it."""
     identifier: int
@@ -55,7 +61,7 @@ WORKFLOW = 'libcxx-benchmark-commit.yml'
 # not available from the API) so this format is a contract with the
 # libcxx-benchmark-commit.yml workflow.
 RUN_NAME_PREFIX = '[libc++] Run benchmark suite against '
-RUN_NAME = re.compile(re.escape(RUN_NAME_PREFIX) + r'([0-9a-fA-F]{40}) on (\S+)$')
+RUN_NAME = re.compile(re.escape(RUN_NAME_PREFIX) + r'([0-9a-fA-F]{40}) on (\S+)( \(dry run\))?$')
 
 
 class HelpFormatter(argparse.ArgumentDefaultsHelpFormatter,
@@ -102,14 +108,17 @@ def collapse(items: Sequence[common.WorkItem]) -> List[common.WorkItem]:
     return ordered
 
 
-def target_of_run(title: str) -> Optional[common.Target]:
+def parse_run_name(title: str) -> Optional[RunName]:
     """
-    Return what a workflow run is benchmarking, or None if it can't be told.
+    Return the information encoded in a worfklow's run-name, or None if it can't be parsed.
 
     The name has to match the workflow's `run-name` exactly.
     """
     match = RUN_NAME.match(title.strip())
-    return common.Target(match.group(1).lower(), match.group(2)) if match else None
+    if match is None:
+        return None
+    return RunName(target=common.Target(match.group(1).lower(), match.group(2)),
+                   dry_run=match.group(3) is not None)
 
 
 def connect(token: str, repository: str, workflow: str) -> github.Workflow.Workflow:
@@ -132,19 +141,25 @@ def workflow_runs(workflow: github.Workflow.Workflow) -> List[WorkflowRun]:
 
     Cancelled runs or runs named in any other format are ignored: they either
     predate this tooling or don't represent expended capacity towards benchmarking
-    a target.
+    a target. Dry-runs are ignored too, since they never submit to LNT.
     """
     runs: Dict[int, WorkflowRun] = {}
+    dry: Set[int] = set()
     try:
         for run in workflow.get_runs():
-            target = target_of_run(run.display_title) if run.display_title else None
-            if target is None or run.conclusion == 'cancelled':
+            parsed = parse_run_name(run.display_title) if run.display_title else None
+            if parsed is None or run.conclusion == 'cancelled':
+                continue
+            if parsed.dry_run:
+                dry.add(run.id)
                 continue
             # Deduplicate by id: pages can overlap while runs are being created.
-            runs[run.id] = WorkflowRun(identifier=run.id, target=target,
+            runs[run.id] = WorkflowRun(identifier=run.id, target=parsed.target,
                                        finished=run.status == 'completed')
     except github.GithubException as error:
         raise GithubError(f'could not list the runs of {workflow.path}: {error}')
+    if dry:
+        logging.info(f'ignoring {len(dry)} dry runs')
     return list(runs.values())
 
 
@@ -242,9 +257,10 @@ def workflow_inputs(args: argparse.Namespace, item: common.WorkItem) -> Dict[str
     """Return the inputs to dispatch the workflow with for a work item."""
     inputs = {'commit': item.commit,
               'lnt-machine': item.machine,
-              # Submission is not optional: a run whose results are not recorded
-              # anywhere would be requested again on every future invocation.
-              # During a dry run nothing runs, so nothing is submitted either.
+              # Submitting to LNT is mandatory, since a run whose results are not recorded
+              # anywhere would be requested again on every future invocation. When run
+              # with --dry-run, this tool never actually dispatches the workflow with
+              # `submit-lnt: false`.
               'submit-lnt': 'false' if args.dry_run else 'true'}
     if args.lnt_url:
         inputs['lnt-url'] = args.lnt_url