Optimize testing of interesting commits

It's now taking 1 hour (!) to check all entries in
interesting-commits/linux.  This time is spent in --is-ancestor
checks.  With the list of interesting commits growing over time
we either need to trim it from time to time, so optimize processing.

This patch does 2 optimizations:
- the obvious optimization to break from loop on first match
- the optimization to quickly check whether commit is inside
  the bisict range.

Change-Id: I712e08970a65e26a517571240e2a513878c907bb

1 files changed, 19 insertions, 0 deletions

diff --git a/round-robin-bisect.sh b/round-robin-bisect.sh
index 7a48bf0e..24155b7b 100755
--- a/round-robin-bisect.sh
+++ b/round-robin-bisect.sh
@@ -344,6 +344,11 @@ print_tested_revs ()
 # Try to reduce bisection range by testing regressions (and their parents)
 # identified in other configurations.
 touch ../interesting-commits/$current_project
+# Generate list of commits inside the bisection range.
+# It's surprising how expensive beloow "--is-ancestor" checks are, and it's
+# a good optimization to skip commits outside of our bisect range quickly.
+commits_to_test=$artifacts/git-logs/commits_to_test
+git bisect view --pretty=%H > $commits_to_test
 # This loop can generate lots of console noise.
 set +x
 while [ x"$(get_first_bad </dev/null)" = x"" ] && read -a arr; do
@@ -351,6 +356,13 @@ while [ x"$(get_first_bad </dev/null)" = x"" ] && read -a arr; do
     set -euf -o pipefail
 
     sha1="${arr[0]}"
+
+    if ! grep -q "^$sha1\$" $commits_to_test; then
+	# Commit is outside of bisection range.
+	# shellcheck disable=SC2106
+	continue
+    fi
+
     # Skip $bad_rev and $baseline_rev, these were already tested.
     if git bisect log | grep -q "^git bisect .* $sha1\$"; then
 	# shellcheck disable=SC2106
@@ -364,11 +376,17 @@ while [ x"$(get_first_bad </dev/null)" = x"" ] && read -a arr; do
     for tested_bad in $(print_tested_revs bad); do
 	if ! git merge-base --is-ancestor $sha1 $tested_bad; then
 	    skip=true
+	    break
 	fi
     done
+    if $skip; then
+	# shellcheck disable=SC2106
+	continue
+    fi
     for tested_good in $(print_tested_revs good); do
 	if git merge-base --is-ancestor $sha1 $tested_good; then
 	    skip=true
+	    break
 	fi
     done
     if $skip; then
@@ -388,6 +406,7 @@ while [ x"$(get_first_bad </dev/null)" = x"" ] && read -a arr; do
     else
 	git bisect bad
     fi
+    git bisect view --pretty=%H > $commits_to_test
     ) </dev/null
 done < <(tac ../interesting-commits/$current_project)
 if $verbose; then set -x; fi