Isolate bigcrawl in a second pass on macOS to parallelize the rest

macOS was the CI bottleneck (~460s serial, the ~8min total): its loopback drops
fetches when bigcrawl's sustained -c8 crawl competes with other crawls, so a
parallel make check flaked bigcrawl's exact file count. Rather than keep the
whole macOS suite serial, run everything except bigcrawl in parallel (2x cores,
capped 16), then bigcrawl alone in a second pass, which is the serial-safe
condition green on master. Linux still runs the full suite in parallel.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

.github/workflows/ci.yml

@@ -55,7 +55,9 @@ jobs:
         run: make -j"$(nproc)"
 
       - name: Test
-        run: make check
+        run: |
+          jobs=$(( $(nproc) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          make check -j"$jobs"
 
       - name: Print the test log on failure
         if: failure()
@@ -99,7 +101,8 @@ jobs:
           sudo find /usr/bin /usr/local/bin -maxdepth 1 -name 'python3*' \
             -exec mv {} {}.hidden \;
           ! command -v python3
-          make check
+          jobs=$(( $(nproc) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          make check -j"$jobs"
 
       - name: Print the test log on failure
         if: failure()
@@ -133,7 +136,15 @@ jobs:
         run: make -j"$(sysctl -n hw.ncpu)"
 
       - name: Test
-        run: make check
+        # bigcrawl's sustained -c8 crawl drops fetches on macOS's loopback when
+        # it competes with other crawls, flaking its exact file count (the #527
+        # macOS drop). Run everything else in parallel, then bigcrawl alone (its
+        # serial-safe condition). Linux tolerates the full parallel run.
+        run: |
+          jobs=$(( $(sysctl -n hw.ncpu) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          rest=$(cd tests && ls *.test | grep -v '^36_local-bigcrawl\.test$' | tr '\n' ' ')
+          make check -j"$jobs" TESTS="$rest"
+          make check TESTS=36_local-bigcrawl.test
 
       - name: Print the test log on failure
         if: failure()
@@ -171,7 +182,9 @@ jobs:
         run: make -j"$(nproc)"
 
       - name: Test
-        run: make check
+        run: |
+          jobs=$(( $(nproc) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          make check -j"$jobs"
 
       - name: Print the test log on failure
         if: failure()
@@ -226,7 +239,9 @@ jobs:
         env:
           ASAN_OPTIONS: detect_leaks=0:abort_on_error=1:halt_on_error=1:strict_string_checks=1:malloc_fill_byte=202:max_malloc_fill_size=2147483647:free_fill_byte=203:max_free_fill_size=2147483647
           UBSAN_OPTIONS: print_stacktrace=1:halt_on_error=1
-        run: make check
+        run: |
+          jobs=$(( $(nproc) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          make check -j"$jobs"
 
       - name: Print the test log on failure
         if: failure()
@@ -272,7 +287,8 @@ jobs:
           # 01_engine-* only; zlib-dependent self-tests are named 01_zlib-* and
           # skipped here (uninstrumented libz floods MSan with false positives).
           tests="$(cd tests && ls 01_engine-*.test | tr '\n' ' ')"
-          make check TESTS="$tests"
+          jobs=$(( $(nproc) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          make check -j"$jobs" TESTS="$tests"
 
       - name: Print the test log on failure
         if: failure()
@@ -347,7 +363,9 @@ jobs:
         run: make -j"$(nproc)"
 
       - name: Test
-        run: make check
+        run: |
+          jobs=$(( $(nproc) * 2 )); [ "$jobs" -le 16 ] || jobs=16
+          make check -j"$jobs"
 
       - name: Print the test log on failure
         if: failure()

AGENTS.md

@@ -6,8 +6,19 @@ the operational checklist: toolchain, invariants, and how to ship a change.
 ## Build & test
 - Fresh clone first: `git submodule update --init src/coucal`
 - `./bootstrap` (regenerates `configure` via `autoreconf`; needs autoconf,
-  automake, libtool), then `bash configure && make && make check`. Or run
-  `sh build.sh` to do bootstrap + configure + make in one shot.
+  automake, libtool), then `bash configure && make -j"$(nproc)" && make check
+  -j"$(nproc)"`. Always pass `-j` to `make check`: the suite runs under
+  automake's parallel harness and each crawl test binds its own ephemeral-port
+  server, so `-j` never contends and a multi-minute serial run drops to
+  seconds. A new `.test` added to `$(TESTS)` is scheduled onto a free worker
+  automatically; only a test slower than the current longest raises the floor.
+  On a few-core Linux box, `-j` at 2x the core count is faster still: the tests
+  spend much of their wall time asleep (server trickles, httrack self-pacing),
+  so an idle core covers a sleeping one. CI uses `min(2*cores, 16)`. macOS runs
+  36_local-bigcrawl alone in a second pass: its sustained `-c8` crawl overloads
+  the macOS loopback when it competes with other crawls and flakes its exact
+  file count (Linux tolerates the full parallel run).
+  Or run `sh build.sh` to do bootstrap + configure + make in one shot.
 
 ## Hard invariants
 - **Generated autotools files are NOT in git.** `configure`, every