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| author | Michael Anthony Knyszek <mknyszek@google.com> | 2021-10-18 19:01:33 +0000 |
|---|---|---|
| committer | Michael Knyszek <mknyszek@google.com> | 2021-11-05 17:46:41 +0000 |
| commit | f063e0da28d441065d36f7d676f86d478f67db1f (patch) | |
| tree | fe9b9eb65be12c6d21f37058edcd12050968782b /src/runtime/mem_linux.go | |
| parent | 4f543b59c5618abccf0e78a17a2aeb173c085a91 (diff) | |
| download | go-f063e0da28d441065d36f7d676f86d478f67db1f.tar.xz | |
runtime: add harddecommit GODEBUG flag
This change adds a new debug flag that makes the runtime map pages
PROT_NONE in sysUnused on Linux, in addition to the usual madvise calls.
This behavior mimics the behavior of decommit on Windows, and is helpful
in debugging the scavenger. sysUsed is also updated to re-map the pages
as PROT_READ|PROT_WRITE, mimicing Windows' explicit commit behavior.
Change-Id: Iaac5fcd0e6920bd1d0e753dd4e7f0c0b128fe842
Reviewed-on: https://go-review.googlesource.com/c/go/+/356612
Trust: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Diffstat (limited to 'src/runtime/mem_linux.go')
| -rw-r--r-- | src/runtime/mem_linux.go | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/src/runtime/mem_linux.go b/src/runtime/mem_linux.go index 3436851091..f8f9c53170 100644 --- a/src/runtime/mem_linux.go +++ b/src/runtime/mem_linux.go @@ -114,9 +114,29 @@ func sysUnused(v unsafe.Pointer, n uintptr) { atomic.Store(&adviseUnused, _MADV_DONTNEED) madvise(v, n, _MADV_DONTNEED) } + + if debug.harddecommit > 0 { + p, err := mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_FIXED|_MAP_PRIVATE, -1, 0) + if p != v || err != 0 { + throw("runtime: cannot disable permissions in address space") + } + } } func sysUsed(v unsafe.Pointer, n uintptr) { + if debug.harddecommit > 0 { + p, err := mmap(v, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_FIXED|_MAP_PRIVATE, -1, 0) + if err == _ENOMEM { + throw("runtime: out of memory") + } + if p != v || err != 0 { + throw("runtime: cannot remap pages in address space") + } + return + + // Don't do the sysHugePage optimization in hard decommit mode. + // We're breaking up pages everywhere, there's no point. + } // Partially undo the NOHUGEPAGE marks from sysUnused // for whole huge pages between v and v+n. This may // leave huge pages off at the end points v and v+n |