commit 30940cfad6c45d40bec377aeacc10f6964e75b76
author Dmitriy Vyukov <dvyukov@google.com> Mon Aug 18 16:33:39 2014 +0400
committer Dmitriy Vyukov <dvyukov@google.com> Mon Aug 18 16:33:39 2014 +0400
tree 4c77829d193bc35b4fb99d293670a81624253375
parent c6fe53a230e70bbb7a5582afe96cacf174eb0335

runtime: don't acquirem on malloc fast path
Mallocgc must be atomic wrt GC, but for performance reasons
don't acquirem/releasem on fast path. The code does not have
split stack checks, so it can't be preempted by GC.
Functions like roundup/add are inlined. And onM/racemalloc are nosplit.
Also add debug code that checks these assumptions.

benchmark                     old ns/op     new ns/op     delta
BenchmarkMalloc8              20.5          17.2          -16.10%
BenchmarkMalloc16             29.5          27.0          -8.47%
BenchmarkMallocTypeInfo8      31.5          27.6          -12.38%
BenchmarkMallocTypeInfo16     34.7          30.9          -10.95%

LGTM=khr
R=golang-codereviews, khr
CC=golang-codereviews, rlh, rsc
https://golang.org/cl/123100043