runtime: reorganize memory code

Move code from malloc1.go, malloc2.go, mem.go, mgc0.go into
appropriate locations.

Factor mgc.go into mgc.go, mgcmark.go, mgcsweep.go, mstats.go.

A lot of this code was in certain files because the right place was in
a C file but it was written in Go, or vice versa. This is one step toward
making things actually well-organized again.

Change-Id: I6741deb88a7cfb1c17ffe0bcca3989e10207968f
Reviewed-on: https://go-review.googlesource.com/5300
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Rick Hudson <rlh@golang.org>

1 files changed, 28 insertions, 0 deletions

diff --git a/src/runtime/mfixalloc.go b/src/runtime/mfixalloc.go
index 3934a9e439..c1106b6281 100644
--- a/src/runtime/mfixalloc.go
+++ b/src/runtime/mfixalloc.go
@@ -10,6 +10,34 @@ package runtime
 
 import "unsafe"
 
+// FixAlloc is a simple free-list allocator for fixed size objects.
+// Malloc uses a FixAlloc wrapped around sysAlloc to manages its
+// MCache and MSpan objects.
+//
+// Memory returned by FixAlloc_Alloc is not zeroed.
+// The caller is responsible for locking around FixAlloc calls.
+// Callers can keep state in the object but the first word is
+// smashed by freeing and reallocating.
+type fixalloc struct {
+	size   uintptr
+	first  unsafe.Pointer // go func(unsafe.pointer, unsafe.pointer); f(arg, p) called first time p is returned
+	arg    unsafe.Pointer
+	list   *mlink
+	chunk  *byte
+	nchunk uint32
+	inuse  uintptr // in-use bytes now
+	stat   *uint64
+}
+
+// A generic linked list of blocks.  (Typically the block is bigger than sizeof(MLink).)
+// Since assignments to mlink.next will result in a write barrier being preformed
+// this can not be used by some of the internal GC structures. For example when
+// the sweeper is placing an unmarked object on the free list it does not want the
+// write barrier to be called since that could result in the object being reachable.
+type mlink struct {
+	next *mlink
+}
+
 // Initialize f to allocate objects of the given size,
 // using the allocator to obtain chunks of memory.
 func fixAlloc_Init(f *fixalloc, size uintptr, first func(unsafe.Pointer, unsafe.Pointer), arg unsafe.Pointer, stat *uint64) {