From a6083e555cb6dbe43c616126fb52d5d0565a14ab Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Motiejus=20Jak=C5=A1tys?= <motiejus@jakstys.lt>
Date: Sun, 11 Dec 2022 15:55:21 +0200
Subject: [PATCH] tests with sysroot

---
 README.md | 33 +++++++++++++++++++--------------
 WORKSPACE | 33 +++++++++++++++++++++++++++++++--
 2 files changed, 50 insertions(+), 16 deletions(-)

diff --git a/README.md b/README.md
index 2be5d94..b7f4840 100644
--- a/README.md
+++ b/README.md
@@ -28,30 +28,35 @@ bazel --batch clean; bazel --batch build --spawn_strategy=local  --platforms=@zi
 INFO: Elapsed time: 17.021s, Critical Path: 1.67s
 ```
 
-zig cc with `--sandbox_base=/dev/shm`: all sandbox files, including the
-zig_sdk, are put to `/dev/shm`. However, they are all symlinks, which means zig
-will re-hash all it's dependencies. 42 seconds:
-
-```
-bazel --batch clean; bazel --batch build --sandbox_base=/dev/shm --platforms=@zig_sdk//libc_aware/platform:linux_amd64_gnu.2.28 ...
-INFO: Elapsed time: 42.251s, Critical Path: 5.26s
-```
-
-zig cc plain: 142 seconds. Sandbox is on a real disk, which means it will take
+zig cc plain: 61 seconds. Sandbox is on a real disk, which means it will take
 even longer to re-hash all its dependencies:
 
 ```
 bazel --batch clean; bazel --batch build --platforms=@zig_sdk//libc_aware/platform:linux_amd64_gnu.2.28 ...
-INFO: Elapsed time: 142.264s, Critical Path: 20.65s
+INFO: Elapsed time: 61.128s, Critical Path: 8.35s
 ```
 
-Similar to `--config=hermetic-sandbox`. Which means there is something else at
-play, not only re-hashing the sandbox files:
+zig cc with hardlinks: `--config=hermetic-sandbox`. This uses hardlinks to
+zig_sdk instead of symlinks:
 
 ```
 bazel --batch clean; bazel --batch build --config=hermetic-sandbox --platforms=@zig_sdk//libc_aware/platform:linux_amd64_gnu.2.28 ...
-INFO: Elapsed time: 136.957s, Critical Path: 18.14s
+INFO: Elapsed time: 45.886s, Critical Path: 9.56s
 ```
 
+llvm with sysroot (this sysroot is about half the size of zig):
+
+```
+bazel --batch clean; bazel --batch build --config=hermetic-sandbox --extra_toolchains=@llvm_toolchain_with_sysroot//:cc-toolchain-x86_64-linux ...
+INFO: Elapsed time: 25.644s, Critical Path: 3.03s
+```
+
+Flame graphs and discussion
+---------------------------
+
+Flame graphs are in results/. As of 2022-12-11 most of the overhead comes from
+creating and deleting the sandboxes. Time for a new sandboxfs!
+
+
 [1]: https://sr.ht/~motiejus/bazel-zig-cc
 [2]: https://github.com/grailbio/bazel-toolchain
diff --git a/WORKSPACE b/WORKSPACE
index e04c031..fd147aa 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -19,12 +19,41 @@ bazel_toolchain_dependencies()
 
 load("@com_grail_bazel_toolchain//toolchain:rules.bzl", "llvm_toolchain")
 
+
+LLVM_VERSION = "14.0.0"
+
 llvm_toolchain(
     name = "llvm_toolchain",
-    llvm_version = "14.0.0",
+    llvm_version = LLVM_VERSION,
 )
 
-load("@llvm_toolchain//:toolchains.bzl", "llvm_register_toolchains")
+# This sysroot is used by github.com/vsco/bazel-toolchains.
+http_archive(
+    name = "org_chromium_sysroot_linux_x64",
+    build_file_content = """
+filegroup(
+  name = "sysroot",
+  srcs = glob(["*/**"]),
+  visibility = ["//visibility:public"],
+)
+""",
+    sha256 = "84656a6df544ecef62169cfe3ab6e41bb4346a62d3ba2a045dc5a0a2ecea94a3",
+    urls = ["https://commondatastorage.googleapis.com/chrome-linux-sysroot/toolchain/2202c161310ffde63729f29d27fe7bb24a0bc540/debian_stretch_amd64_sysroot.tar.xz"],
+)
+
+llvm_toolchain(
+    name = "llvm_toolchain_with_sysroot",
+    llvm_version = LLVM_VERSION,
+    sysroot = {
+        "linux-x86_64": "@org_chromium_sysroot_linux_x64//:sysroot",
+    },
+    # We can share the downloaded LLVM distribution with the first configuration.
+    toolchain_roots = {
+        "": "@llvm_toolchain_llvm//",
+    },
+)
+
+load("@llvm_toolchain_with_sysroot//:toolchains.bzl", "llvm_register_toolchains")
 
 #llvm_register_toolchains()