runtime: add wrappers for sys* functions and consolidate docs

This change lifts all non-platform-specific code out of sys* functions
for each platform up into wrappers, and moves documentation about the OS
virtual memory abstraction layer from malloc.go to mem.go, which
contains those wrappers.

Change-Id: Ie803e4447403eaafc508b34b53a1a47d6cee9388
Reviewed-on: https://go-review.googlesource.com/c/go/+/393398
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Trust: Michael Knyszek <mknyszek@google.com>

1 files changed, 9 insertions, 13 deletions

diff --git a/src/runtime/mem_linux.go b/src/runtime/mem_linux.go
index f8333014c2..980f7bb53d 100644
--- a/src/runtime/mem_linux.go
+++ b/src/runtime/mem_linux.go
@@ -17,7 +17,7 @@ const (
 // Don't split the stack as this method may be invoked without a valid G, which
 // prevents us from allocating more stack.
 //go:nosplit
-func sysAlloc(n uintptr, sysStat *sysMemStat) unsafe.Pointer {
+func sysAllocOS(n uintptr) unsafe.Pointer {
 	p, err := mmap(nil, n, _PROT_READ|_PROT_WRITE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
 	if err != 0 {
 		if err == _EACCES {
@@ -30,13 +30,12 @@ func sysAlloc(n uintptr, sysStat *sysMemStat) unsafe.Pointer {
 		}
 		return nil
 	}
-	sysStat.add(int64(n))
 	return p
 }
 
 var adviseUnused = uint32(_MADV_FREE)
 
-func sysUnused(v unsafe.Pointer, n uintptr) {
+func sysUnusedOS(v unsafe.Pointer, n uintptr) {
 	// By default, Linux's "transparent huge page" support will
 	// merge pages into a huge page if there's even a single
 	// present regular page, undoing the effects of madvise(adviseUnused)
@@ -123,7 +122,7 @@ func sysUnused(v unsafe.Pointer, n uintptr) {
 	}
 }
 
-func sysUsed(v unsafe.Pointer, n uintptr) {
+func sysUsedOS(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 {
@@ -145,10 +144,10 @@ func sysUsed(v unsafe.Pointer, n uintptr) {
 	// the end points as well, but it's probably not worth
 	// the cost because when neighboring allocations are
 	// freed sysUnused will just set NOHUGEPAGE again.
-	sysHugePage(v, n)
+	sysHugePageOS(v, n)
 }
 
-func sysHugePage(v unsafe.Pointer, n uintptr) {
+func sysHugePageOS(v unsafe.Pointer, n uintptr) {
 	if physHugePageSize != 0 {
 		// Round v up to a huge page boundary.
 		beg := alignUp(uintptr(v), physHugePageSize)
@@ -164,16 +163,15 @@ func sysHugePage(v unsafe.Pointer, n uintptr) {
 // Don't split the stack as this function may be invoked without a valid G,
 // which prevents us from allocating more stack.
 //go:nosplit
-func sysFree(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
-	sysStat.add(-int64(n))
+func sysFreeOS(v unsafe.Pointer, n uintptr) {
 	munmap(v, n)
 }
 
-func sysFault(v unsafe.Pointer, n uintptr) {
+func sysFaultOS(v unsafe.Pointer, n uintptr) {
 	mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE|_MAP_FIXED, -1, 0)
 }
 
-func sysReserve(v unsafe.Pointer, n uintptr) unsafe.Pointer {
+func sysReserveOS(v unsafe.Pointer, n uintptr) unsafe.Pointer {
 	p, err := mmap(v, n, _PROT_NONE, _MAP_ANON|_MAP_PRIVATE, -1, 0)
 	if err != 0 {
 		return nil
@@ -181,9 +179,7 @@ func sysReserve(v unsafe.Pointer, n uintptr) unsafe.Pointer {
 	return p
 }
 
-func sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
-	sysStat.add(int64(n))
-
+func sysMapOS(v unsafe.Pointer, n uintptr) {
 	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")