PGO: Don't re-run benchmarks if their results will be discarded.

This moves the "should this be skipped?" logic earlier in the pipeline
so that it can be used prior to running benchmarks at all, which consume
a bunch of machine-hours for no reason if their results will be discarded.

BuildKite doesn't seem to have a way for an intermediate step to mark the
whole pipeline as skippable, so this refactors the skip logic to its own
script that can be used as `skip-or.sh || else_do_this`.
Use it in all steps.

PiperOrigin-RevId: 773103605

Author: EtiennePerot

.buildkite/pgo.yaml

@@ -23,7 +23,7 @@ steps:
     label: ":arrows_counterclockwise: Refresh PGO profiles (x86_64 Systrap)"
     if: build.branch == "master" && build.tag == null
     commands:
-      - make ARCH=x86_64 benchmark-refresh-pgo BENCHMARKS_PLATFORMS=systrap
-      - ./.buildkite/scripts/pgo/commit-update.sh
+      - ./.buildkite/scripts/pgo/maybe-skip.sh --tolerate-no-profile-changes make ARCH=x86_64 benchmark-refresh-pgo BENCHMARKS_PLATFORMS=systrap
+      - ./.buildkite/scripts/pgo/mabe-skip.sh ./.buildkite/scripts/pgo/commit-update.sh
     agents:
       arch: "amd64"

.buildkite/scripts/pgo/commit-update.sh

@@ -16,34 +16,15 @@
 
 set -euxo pipefail
 
-if [[ "$(git status --porcelain | wc -l)" == 0 ]]; then
-  echo "No changes to runsc profiles." >&2
-  exit 0
-fi
-
 today="$(date +"%Y-%m-%d")"
 repo_url="https://github.com/google/gvisor.git"
 pgo_branch_name="pgo/update-${today}"
 
-# If the remote branch already exists, do nothing.
-existing_remote="$(git ls-remote --heads "$repo_url" "refs/heads/${pgo_branch_name}" || true)"
-if [[ -n "$existing_remote" ]]; then
-  echo "Remote branch '$pgo_branch_name' already exists, skipping." >&2
-  exit 0
-fi
-
 # GitHub CLI authentication.
 gh --version
 gh auth login --with-token < "$HOME/.github-token"
 gh auth setup-git
 
-# If there is already an open PR for PGO update, do nothing.
-if [[ "$(gh pr --repo="$repo_url" list --label pgo-update --state open --json title --jq length)" -gt 0 ]]; then
-  echo "There is already an open PR for PGO update, skipping." >&2
-  PAGER=cat gh pr --repo="$repo_url" list --label pgo-update --state open
-  exit 0
-fi
-
 # Create new branch for the PR and stages changes in it.
 git stash
 git pull --rebase=true "$repo_url" master

.buildkite/scripts/pgo/maybe-skip.sh

@@ -0,0 +1,63 @@
+#!/bin/bash
+
+# Copyright 2025 The gVisor Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This script executes the argv it gets as arguments, unless it
+# determines that the PGO profile update should be skipped.
+# Takes the optional argument '--tolerate-no-profile-changes' which can be
+# used to tolerate the case where no profile changes are detected.
+
+set -euxo pipefail
+
+today="$(date +"%Y-%m-%d")"
+repo_url="https://github.com/google/gvisor.git"
+pgo_branch_name="pgo/update-${today}"
+
+tolerate_no_profile_changes=false
+for arg; do
+  if [[ "$arg" == '--tolerate-no-profile-changes' ]]; then
+    tolerate_no_profile_changes=true
+    shift
+  fi
+done
+
+# If the remote branch already exists, do nothing.
+existing_remote="$(git ls-remote --heads "$repo_url" "refs/heads/${pgo_branch_name}" || true)"
+if [[ -n "$existing_remote" ]]; then
+  echo "Remote branch '$pgo_branch_name' already exists, skipping." >&2
+  exit 0
+fi
+
+# GitHub CLI authentication.
+gh --version
+gh auth login --with-token < "$HOME/.github-token"
+gh auth setup-git
+
+# If there is already an open PR for PGO update, do nothing.
+if [[ "$(gh pr --repo="$repo_url" list --label pgo-update --state open --json title --jq length)" -gt 0 ]]; then
+  echo "There is already an open PR for PGO update, skipping." >&2
+  PAGER=cat gh pr --repo="$repo_url" list --label pgo-update --state open
+  exit 0
+fi
+
+if ! echo "$@" | grep -qFe '--tolerate-no-profile-changes'; then
+  if [[ "$(git status --porcelain | wc -l)" == 0 ]]; then
+    echo "No changes to runsc profiles; skipping." >&2
+    exit 0
+  fi
+fi
+
+echo "Running:" "$@" >&2
+exec "$@"