Merge #115585

115585: build: expose knob to disable GC assist r=nvanbenschoten a=nvanbenschoten

Fixes #115584.

This commit updates our patched Go runtime to expose a knob to disable the runtime's GC assist mechanism. The knob is exposed under the `GODEBUG` environment variable, and can be accessed with `GODEBUG=gcnoassist=1`.

For now, this is just meant for experimentation purposes. It will assist us as we look to reduce the impact the GC has on tail latency.

Release note: None

Co-authored-by: Nathan VanBenschoten <nvanbenschoten@gmail.com>

WORKSPACE

@@ -163,13 +163,13 @@ load(
 go_download_sdk(
     name = "go_sdk",
     sdks = {
-        "darwin_amd64": ("go1.21.3.darwin-amd64.tar.gz", "253d8d4b32a1d7731dff1245f009362858a0c685af8f52b671dd906b2c67d78d"),
-        "darwin_arm64": ("go1.21.3.darwin-arm64.tar.gz", "877543c11149341e4954cb2e625deb7974e94c3c77f5f71a24d35e54cb54fb05"),
-        "linux_amd64": ("go1.21.3.linux-amd64.tar.gz", "3b0307b4e91d6b34870ed1d29366aba77cb864dc93b7098cdfb5d4619cb58566"),
-        "linux_arm64": ("go1.21.3.linux-arm64.tar.gz", "c0d2da5e1b9ff93d0e4262189e59586cc0c17c207578429f716de2d5799ba36a"),
-        "windows_amd64": ("go1.21.3.windows-amd64.tar.gz", "c0e2957014e72056ed1c2c080d772d7c8e96a3143f228f6b511231fc31c07593"),
+        "darwin_amd64": ("go1.21.3.darwin-amd64.tar.gz", "85a9bce961b9bd45d6d67e306c79052f739ea9bda99f234ef7a716129315bfc8"),
+        "darwin_arm64": ("go1.21.3.darwin-arm64.tar.gz", "52d8a95622bf29bb73aa49af0ff73955e034969dba46c7f439399af7adafc787"),
+        "linux_amd64": ("go1.21.3.linux-amd64.tar.gz", "3ff4a24c4e64b46a3ade80abdcf34b8c26704799ec2763814e68edd81142df68"),
+        "linux_arm64": ("go1.21.3.linux-arm64.tar.gz", "29b53edd23dbcc27fc421e9cc83a0cd81f1d5e2bf9d061da6907e8be66fff48f"),
+        "windows_amd64": ("go1.21.3.windows-amd64.tar.gz", "d025882e7d846d722a90ca66204b561c6650e127e338fdc22e39964995253224"),
     },
-    urls = ["https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/{}"],
+    urls = ["https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/{}"],
     version = "1.21.3",
 )
 
@@ -641,9 +641,9 @@ distdir_repositories()
 go_download_sdk(
     name = "go_sdk_fips",
     sdks = {
-        "linux_amd64": ("go1.21.3fips.linux-amd64.tar.gz", "216acc2939bf16748ec240ffe1752b442ec098bd9ac5e12ecd44db4ff77e0ab9"),
+        "linux_amd64": ("go1.21.3fips.linux-amd64.tar.gz", "03a3494f7b9d8a63750f72afd4f398baa723509a3c14dbff888a857ca01f0b5c"),
     },
-    urls = ["https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/{}"],
+    urls = ["https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/{}"],
     version = "1.21.3fips",
     # In the golang-fips toolchain, FIPS-ready crypto packages are used by default, regardless of build tags.
     # The boringcrypto experiment does almost nothing in this toolchain, but it does enable the use of the

build/bazelutil/distdir_files.bzl

@@ -1189,12 +1189,12 @@ DISTDIR_FILES = {
     "https://storage.googleapis.com/public-bazel-artifacts/c-deps/20230718-202534/libproj_foreign.macos.20230718-202534.tar.gz": "96771a33542beb72067afcafaeb790134014e56798fa4cbe291894c4ebf8b68d",
     "https://storage.googleapis.com/public-bazel-artifacts/c-deps/20230718-202534/libproj_foreign.macosarm.20230718-202534.tar.gz": "b2c60ffe1f50c6e81ba906f773b95d3a6699538d57e71749579552f4211a1e3e",
     "https://storage.googleapis.com/public-bazel-artifacts/c-deps/20230718-202534/libproj_foreign.windows.20230718-202534.tar.gz": "16de1e76ee8de4bd144dc57bfde05385d086943ca1b64cc246055c8b0cd71c65",
-    "https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/go1.21.3.darwin-amd64.tar.gz": "253d8d4b32a1d7731dff1245f009362858a0c685af8f52b671dd906b2c67d78d",
-    "https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/go1.21.3.darwin-arm64.tar.gz": "877543c11149341e4954cb2e625deb7974e94c3c77f5f71a24d35e54cb54fb05",
-    "https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/go1.21.3.linux-amd64.tar.gz": "3b0307b4e91d6b34870ed1d29366aba77cb864dc93b7098cdfb5d4619cb58566",
-    "https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/go1.21.3.linux-arm64.tar.gz": "c0d2da5e1b9ff93d0e4262189e59586cc0c17c207578429f716de2d5799ba36a",
-    "https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/go1.21.3.windows-amd64.tar.gz": "c0e2957014e72056ed1c2c080d772d7c8e96a3143f228f6b511231fc31c07593",
-    "https://storage.googleapis.com/public-bazel-artifacts/go/20231019-214851/go1.21.3fips.linux-amd64.tar.gz": "216acc2939bf16748ec240ffe1752b442ec098bd9ac5e12ecd44db4ff77e0ab9",
+    "https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/go1.21.3.darwin-amd64.tar.gz": "85a9bce961b9bd45d6d67e306c79052f739ea9bda99f234ef7a716129315bfc8",
+    "https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/go1.21.3.darwin-arm64.tar.gz": "52d8a95622bf29bb73aa49af0ff73955e034969dba46c7f439399af7adafc787",
+    "https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/go1.21.3.linux-amd64.tar.gz": "3ff4a24c4e64b46a3ade80abdcf34b8c26704799ec2763814e68edd81142df68",
+    "https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/go1.21.3.linux-arm64.tar.gz": "29b53edd23dbcc27fc421e9cc83a0cd81f1d5e2bf9d061da6907e8be66fff48f",
+    "https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/go1.21.3.windows-amd64.tar.gz": "d025882e7d846d722a90ca66204b561c6650e127e338fdc22e39964995253224",
+    "https://storage.googleapis.com/public-bazel-artifacts/go/20231205-160258/go1.21.3fips.linux-amd64.tar.gz": "03a3494f7b9d8a63750f72afd4f398baa723509a3c14dbff888a857ca01f0b5c",
     "https://storage.googleapis.com/public-bazel-artifacts/java/railroad/rr-1.63-java8.zip": "d2791cd7a44ea5be862f33f5a9b3d40aaad9858455828ebade7007ad7113fb41",
     "https://storage.googleapis.com/public-bazel-artifacts/js/rules_jest-v0.18.4.tar.gz": "d3bb833f74b8ad054e6bff5e41606ff10a62880cc99e4d480f4bdfa70add1ba7",
     "https://storage.googleapis.com/public-bazel-artifacts/js/rules_js-v1.26.1.tar.gz": "08061ba5e5e7f4b1074538323576dac819f9337a0c7d75aee43afc8ae7cb6e18",

build/teamcity/internal/release/build-and-publish-patched-go/diff.patch

@@ -1,3 +1,31 @@
+diff --git a/src/runtime/extern.go b/src/runtime/extern.go
+index 26dcf0bd52..75865d2868 100644
+--- a/src/runtime/extern.go
++++ b/src/runtime/extern.go
+@@ -85,6 +85,10 @@ It is a comma-separated list of name=val pairs setting these named variables:
+ 	making every garbage collection a stop-the-world event. Setting gcstoptheworld=2
+ 	also disables concurrent sweeping after the garbage collection finishes.
+
++	gcnoassist: setting gcnoassist=1 disables garbage collection assist, minimizing
++	garbage collection overhead for user goroutines at the expense of a higher risk
++	of out-of-memory failures with high allocation rates.
++
+ 	gctrace: setting gctrace=1 causes the garbage collector to emit a single line to standard
+ 	error at each collection, summarizing the amount of memory collected and the
+ 	length of the pause. The format of this line is subject to change. Included in
+diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go
+index 44479cc2be..a24ce64a24 100644
+--- a/src/runtime/malloc.go
++++ b/src/runtime/malloc.go
+@@ -1270,7 +1270,7 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
+ // Returns the G for which the assist credit was accounted.
+ func deductAssistCredit(size uintptr) *g {
+ 	var assistG *g
+-	if gcBlackenEnabled != 0 {
++	if debug.gcnoassist == 0 && gcBlackenEnabled != 0 {
+ 		// Charge the current user G for this allocation.
+ 		assistG = getg()
+ 		if assistG.m.curg != nil {
 diff --git a/src/runtime/proc.go b/src/runtime/proc.go
 index 554a60d747..8d64ee31c8 100644
 --- a/src/runtime/proc.go
@@ -74,6 +102,26 @@ index 554a60d747..8d64ee31c8 100644
 
  	if gcBlackenEnabled != 0 && gp.gcAssistBytes > 0 {
  		// Flush assist credit to the global pool. This gives
+diff --git a/src/runtime/runtime1.go b/src/runtime/runtime1.go
+index 92a7e021ee..2796baf922 100644
+--- a/src/runtime/runtime1.go
++++ b/src/runtime/runtime1.go
+@@ -315,6 +315,7 @@ var debug struct {
+ 	gcpacertrace       int32
+ 	gcshrinkstackoff   int32
+ 	gcstoptheworld     int32
++	gcnoassist         int32
+ 	gctrace            int32
+ 	invalidptr         int32
+ 	madvdontneed       int32 // for Linux; issue 28466
+@@ -348,6 +349,7 @@ var dbgvars = []*dbgVar{
+ 	{name: "gcpacertrace", value: &debug.gcpacertrace},
+ 	{name: "gcshrinkstackoff", value: &debug.gcshrinkstackoff},
+ 	{name: "gcstoptheworld", value: &debug.gcstoptheworld},
++	{name: "gcnoassist", value: &debug.gcnoassist},
+ 	{name: "gctrace", value: &debug.gctrace},
+ 	{name: "invalidptr", value: &debug.invalidptr},
+ 	{name: "madvdontneed", value: &debug.madvdontneed},
 diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
 index f4c76abd1c..57672bd8c5 100644
 --- a/src/runtime/runtime2.go

build/teamcity/internal/release/build-and-publish-patched-go/impl-fips.sh

@@ -34,3 +34,5 @@ GOVERS=$(go/bin/go env GOVERSION)
 GOOS=$(go/bin/go env GOOS)
 GOARCH=$(go/bin/go env GOARCH)
 tar cf - go | gzip -9 > /artifacts/$GOVERS.$GOOS-$GOARCH.tar.gz
+
+sha256sum /artifacts/$GOVERS.$GOOS-$GOARCH.tar.gz