devtool: Add flag to build to allow compiling arbitrary revisions

Passing `--rev` to `tools/devtool build` will do a checkout of the
specified revision into a temporary directory, compile firecracker into
it, and then copy over the final binaries into build/$revision.

This has advantages over our current approach for compiling A/B
revisions, as by only copying the final binaries into build/$revision we
save a lot of bandwidth when uploading artifacts for transfer between
different buildkite steps (as we no longer include gigabytes of
compilation artifacts).

This now means that all revisions are compiled in the same docker
container, however due to the rust-toolchain.toml this should not have
an impact on cross-toolchain testability, and has the advantage that the
cargo cache is shared (meaning we're hitting crates.io for downloads
less).

Signed-off-by: Patrick Roy <[email protected]>

Author: roypat

.buildkite/common.py

@@ -180,16 +180,7 @@ def random_str(k: int):
 
 def ab_revision_build(revision):
     """Generate steps for building an A/B-test revision"""
-    # Copied from framework/ab_test. Double dollar signs needed for Buildkite (otherwise it will try to interpolate itself)
-    return [
-        f"commitish={revision}",
-        f"if ! git cat-file -t $$commitish; then commitish=origin/{revision}; fi",
-        "branch_name=tmp-$$commitish",
-        "git branch $$branch_name $$commitish",
-        f"git clone -b $$branch_name . build/{revision}",
-        f"cd build/{revision} && ./tools/devtool -y build --release && cd -",
-        "git branch -D $$branch_name",
-    ]
+    return [f"./tools/devtool -y build --rev {revision} --release"]
 
 
 def shared_build():

.buildkite/pipeline_perf.py

@@ -98,7 +98,9 @@
     pytest_opts = ""
     if REVISION_A:
         devtool_opts += " --ab"
-        pytest_opts = f"{ab_opts} run build/{REVISION_A}/build/cargo_target/$(uname -m)-unknown-linux-musl/release build/{REVISION_B}/build/cargo_target/$(uname -m)-unknown-linux-musl/release --test {test_path}"
+        pytest_opts = (
+            f"{ab_opts} run build/{REVISION_A}/ build/{REVISION_B} --test {test_path}"
+        )
     else:
         # Passing `-m ''` below instructs pytest to collect tests regardless of
         # their markers (e.g. it will collect both tests marked as nonci, and

tests/framework/ab_test.py

@@ -101,14 +101,15 @@ def git_ab_test(
     return result_a, result_b, comparison
 
 
+DEFAULT_A_DIRECTORY = FC_WORKSPACE_DIR / "build" / "main"
 DEFAULT_B_DIRECTORY = FC_WORKSPACE_DIR / "build" / "cargo_target" / DEFAULT_TARGET_DIR
 
 
 def binary_ab_test(
     test_runner: Callable[[Path, bool], T],
     comparator: Callable[[T, T], U] = default_comparator,
     *,
-    a_directory: Path,
+    a_directory: Path = DEFAULT_A_DIRECTORY,
     b_directory: Path = DEFAULT_B_DIRECTORY,
 ):
     """

tools/ab_test.py

@@ -155,7 +155,7 @@ def load_data_series(report_path: Path, tag=None, *, reemit: bool = False):
 
 def collect_data(binary_dir: Path, tests: list[str]):
     """Executes the specified test using the provided firecracker binaries"""
-    # Example binary_dir: ../build/main/build/cargo_target/x86_64-unknown-linux-musl/release
+    binary_dir = binary_dir.resolve()
 
     print(f"Collecting samples with {binary_dir}")
     subprocess.run(

tools/devtool

@@ -446,12 +446,14 @@ cmd_build() {
     profile="debug"
     libc="musl"
 
+
     # Parse any command line args.
     while [ $# -gt 0 ]; do
         case "$1" in
             "-h"|"--help")  { cmd_help; exit 1;     } ;;
             "--debug")      { profile="debug";      } ;;
             "--release")    { profile="release";    } ;;
+            "--rev")       { shift; revision=$1; } ;;
             "--ssh-keys")
                 shift
                 [[ -z "$1" ]] && \
@@ -489,16 +491,40 @@ cmd_build() {
         extra_args="--volume $host_pub_key_path:$PUB_KEY_PATH:z \
                     --volume $host_priv_key_path:$PRIV_KEY_PATH:z"
 
+    workdir="$CTR_FC_ROOT_DIR"
+    if [ ! -z "$revision" ]; then
+      commitish="$revision"
+      if ! git cat-file -t "$commitish"; then commitish=origin/"$revision"; fi
+      branch_name=tmp-$commitish
+
+      tmp_dir=$(mktemp -d)
+
+      git branch $branch_name $commitish
+      git clone -b $branch_name . $tmp_dir
+      pushd $tmp_dir
+      workdir=$tmp_dir
+      extra_args="$extra_args --volume $tmp_dir:$tmp_dir:z"
+    fi
+
     # Run the cargo build process inside the container.
     # We don't need any special privileges for the build phase, so we run the
     # container as the current user/group.
     run_devctr \
         --user "$(id -u):$(id -g)" \
-        --workdir "$CTR_FC_ROOT_DIR" \
+        --workdir "$workdir" \
         ${extra_args} \
         -- \
         ./tools/release.sh --libc $libc --profile $profile
     ret=$?
+
+    if [ ! -z "$revision" ]; then
+      popd
+      git branch -D $branch_name
+      mkdir -p build/"$revision"
+      cp $tmp_dir/build/cargo_target/$(uname -m)-unknown-linux-$libc/$profile/* build/"$revision"
+      rm -rf $tmp_dir
+    fi
+
     return $ret
 }