ci: Use a RAM disk and more CPUs on FreeBSD.

Run the tests in a RAM disk.  It's still a UFS file system and is backed
by 20GB of disk, but this avoids a lot of I/O.  Even though we disable
fsync, our tests do a lot of directory manipulations, some of which
force file system meta-data to disk and flush slow device write caches
on UFS.  This was a bottleneck preventing effective scaling beyond 2
CPUs.

Now we can use 4 CPUs like on other OSes, for a huge speedup.

Reviewed-by: Maxim Orlov <orlovmg@gmail.com>
Discussion: https://postgr.es/m/CA%2BhUKG%2BFXLcEg1dyTqJjDiNQ8pGom4KrJj4wF38C90thti9dVA%40mail.gmail.com

.cirrus.tasks.yml

@@ -126,11 +126,9 @@ task:
   name: FreeBSD - 13 - Meson
 
   env:
-    # FreeBSD on GCP is slow when running with larger number of CPUS /
-    # jobs. Using one more job than cpus seems to work best.
-    CPUS: 2
-    BUILD_JOBS: 3
-    TEST_JOBS: 3
+    CPUS: 4
+    BUILD_JOBS: 4
+    TEST_JOBS: 8
     IMAGE_FAMILY: pg-ci-freebsd-13
     DISK_SIZE: 50
 

src/tools/ci/gcp_freebsd_repartition.sh

@@ -3,26 +3,24 @@
 set -e
 set -x
 
-# The default filesystem on freebsd gcp images is very slow to run tests on,
-# due to its 32KB block size
-#
-# XXX: It'd probably better to fix this in the image, using something like
-# https://people.freebsd.org/~lidl/blog/re-root.html
-
 # fix backup partition table after resize
 gpart recover da0
 gpart show da0
-# kill swap, so we can delete a partition
-swapoff -a || true
-# (apparently we can only have 4!?)
-gpart delete -i 3 da0
-gpart add -t freebsd-ufs -l data8k -a 4096 da0
-gpart show da0
-newfs -U -b 8192 /dev/da0p3
 
-# Migrate working directory
+# delete and re-add swap partition with expanded size
+swapoff -a
+gpart delete -i 3 da0
+gpart add -t freebsd-swap -l swapfs -a 4096 da0
+gpart show da0
+swapon -a
+
+# create a file system on a memory disk backed by swap, to minimize I/O
+mdconfig -a -t swap -s20g -u md1
+newfs -b 8192 -U /dev/md1
+
+# migrate working directory
 du -hs $CIRRUS_WORKING_DIR
 mv $CIRRUS_WORKING_DIR $CIRRUS_WORKING_DIR.orig
 mkdir $CIRRUS_WORKING_DIR
-mount -o noatime /dev/da0p3 $CIRRUS_WORKING_DIR
+mount -o noatime /dev/md1 $CIRRUS_WORKING_DIR
 cp -r $CIRRUS_WORKING_DIR.orig/* $CIRRUS_WORKING_DIR/