diff options
| author | Austin Clements <austin@google.com> | 2018-01-01 17:53:59 -0500 |
|---|---|---|
| committer | Austin Clements <austin@google.com> | 2018-02-15 21:12:25 +0000 |
| commit | 90666b8a3d5545f4295d9c2517ad607ce5d45e52 (patch) | |
| tree | 4242490e9767d717bbc001676af60f290cd08f48 /src/runtime/malloc.go | |
| parent | 51ae88ee2f9a1063c272a497527751d786291c89 (diff) | |
| download | go-90666b8a3d5545f4295d9c2517ad607ce5d45e52.tar.xz | |
runtime: move comment about address space sizes to malloc.go
Currently there's a detailed comment in lfstack_64bit.go about address
space limitations on various architectures. Since that's now relevant
to malloc, move it to a more prominent place in the documentation for
memLimitBits.
Updates #10460.
Change-Id: If9708291cf3a288057b8b3ba0ba6a59e3602bbd6
Reviewed-on: https://go-review.googlesource.com/85889
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
Diffstat (limited to 'src/runtime/malloc.go')
| -rw-r--r-- | src/runtime/malloc.go | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/src/runtime/malloc.go b/src/runtime/malloc.go index a397382291..f3e738116c 100644 --- a/src/runtime/malloc.go +++ b/src/runtime/malloc.go @@ -160,7 +160,24 @@ const ( // // On 64-bit platforms, we limit this to 48 bits because that // is the maximum supported by Linux across all 64-bit - // architectures, with the exception of s390x. + // architectures, with the exception of s390x. Based on + // processor.h: + // + // Architecture Name Maximum Value (exclusive) + // --------------------------------------------------------------------- + // amd64 TASK_SIZE_MAX 0x007ffffffff000 (47 bit addresses) + // arm64 TASK_SIZE_64 0x01000000000000 (48 bit addresses) + // ppc64{,le} TASK_SIZE_USER64 0x00400000000000 (46 bit addresses) + // mips64{,le} TASK_SIZE64 0x00010000000000 (40 bit addresses) + // s390x TASK_SIZE 1<<64 (64 bit addresses) + // + // These values may increase over time. In particular, ppc64 + // and mips64 support arbitrary 64-bit addresses in hardware, + // but Linux imposes the above limits. amd64 has hardware + // support for 57 bit addresses as of 2017 (56 bits for user + // space), but Linux only uses addresses above 1<<47 for + // mappings that explicitly pass a high hint address. + // // s390x supports full 64-bit addresses, but the allocator // will panic in the unlikely event we exceed 48 bits. // |