diff options
| author | Hans <hzb153@gmail.com> | 2021-08-02 05:43:29 +0000 |
|---|---|---|
| committer | Austin Clements <austin@google.com> | 2021-09-02 13:53:25 +0000 |
| commit | 4591f49938aedbbac7a24225047984479abe72b8 (patch) | |
| tree | abf1430b9e594884ce30346afec34b858aa00653 /src/runtime/mfixalloc.go | |
| parent | a35c5c98c0487f93d70b468483f2ca8e0d698bb7 (diff) | |
| download | go-4591f49938aedbbac7a24225047984479abe72b8.tar.xz | |
runtime: do not alloc never used tail bytes in fixalloc
Currently, the '_FixAllocChunk % fixalloc.size' tail bytes
will never be used when allocing from persistentalloc.
Wasted bytes on darwin/amd64:
_FixAllocChunk % mheap_.spanalloc.size = 64
_FixAllocChunk % mheap_.cachealloc.size = 784
_FixAllocChunk % mheap_.specialfinalizeralloc.size = 16
_FixAllocChunk % mheap_.specialprofilealloc.size = 16
_FixAllocChunk % mheap_.specialReachableAlloc.size = 16
_FixAllocChunk % mheap_.arenaHintAlloc.size = 16
After this commit, fixalloc alloc '_FixAllocChunk / fixalloc.size'
objects exactly with zero waste. Sizeof(fixalloc{}) is unchanged.
Change-Id: Ifc551f5b7aa9d842fa559abbe532ffcfb4d3540c
GitHub-Last-Rev: e08b4c66b82bc7be9d14fb7eb7580504d777481e
GitHub-Pull-Request: golang/go#47439
Reviewed-on: https://go-review.googlesource.com/c/go/+/338090
Reviewed-by: Austin Clements <austin@google.com>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Trust: Cherry Mui <cherryyz@google.com>
Diffstat (limited to 'src/runtime/mfixalloc.go')
| -rw-r--r-- | src/runtime/mfixalloc.go | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/src/runtime/mfixalloc.go b/src/runtime/mfixalloc.go index a81139a389..b701a09b40 100644 --- a/src/runtime/mfixalloc.go +++ b/src/runtime/mfixalloc.go @@ -30,7 +30,8 @@ type fixalloc struct { arg unsafe.Pointer list *mlink chunk uintptr // use uintptr instead of unsafe.Pointer to avoid write barriers - nchunk uint32 + nchunk uint32 // bytes remaining in current chunk + nalloc uint32 // size of new chunks in bytes inuse uintptr // in-use bytes now stat *sysMemStat zero bool // zero allocations @@ -63,6 +64,7 @@ func (f *fixalloc) init(size uintptr, first func(arg, p unsafe.Pointer), arg uns f.list = nil f.chunk = 0 f.nchunk = 0 + f.nalloc = uint32(_FixAllocChunk / size * size) // Round _FixAllocChunk down to an exact multiple of size to eliminate tail waste f.inuse = 0 f.stat = stat f.zero = true @@ -84,8 +86,8 @@ func (f *fixalloc) alloc() unsafe.Pointer { return v } if uintptr(f.nchunk) < f.size { - f.chunk = uintptr(persistentalloc(_FixAllocChunk, 0, f.stat)) - f.nchunk = _FixAllocChunk + f.chunk = uintptr(persistentalloc(uintptr(f.nalloc), 0, f.stat)) + f.nchunk = f.nalloc } v := unsafe.Pointer(f.chunk) |