| commit | 390ffce7d60abf7d5317c0a78beef64affd0059a | [log] [tgz] |
|---|---|---|
| author | Michael Anthony Knyszek <mknyszek@google.com> | Fri Mar 21 16:26:15 2025 +0000 |
| committer | Carlos Amedee <carlos@golang.org> | Thu Jul 10 10:03:34 2025 -0700 |
| tree | 19b721971a3d29673944aea10e80b7fd94756cb1 | |
| parent | b454859a8a1c8ae10635825beda4cf516d949e48 [diff] |
[release-branch.go1.24] runtime: prevent unnecessary zeroing of large objects with pointers CL 614257 refactored mallocgc but lost an optimization: if a span for a large object is already backed by memory fresh from the OS (and thus zeroed), we don't need to zero it. CL 614257 unconditionally zeroed spans for large objects that contain pointers. This change restores the optimization from before CL 614257, which seems to matter in some real-world programs. While we're here, let's also fix a hole with the garbage collector being able to observe uninitialized memory of the large object is observed by the conservative scanner before being published. The gory details are in a comment in heapSetTypeLarge. In short, this change makes span.largeType an atomic variable, such that the GC can only observe initialized memory if span.largeType != nil. For #72991. Fixes #73800. Change-Id: I2048aeb220ab363d252ffda7d980b8788e9674dc Reviewed-on: https://go-review.googlesource.com/c/go/+/659956 Reviewed-by: Keith Randall <khr@golang.org> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Felix Geisendörfer <felix.geisendoerfer@datadoghq.com> (cherry picked from commit df9888ea4e97feb755e452609be5078686370995) Reviewed-on: https://go-review.googlesource.com/c/go/+/682356
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