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package memsize
import (
"bytes"
"fmt"
"reflect"
"sort"
"strings"
"text/tabwriter"
"unsafe"
)
// Scan traverses all objects reachable from v and counts how much memory
// is used per type. The value must be a non-nil pointer to any value.
func Scan(v interface{}) Sizes {
rv := reflect.ValueOf(v)
if rv.Kind() != reflect.Ptr || rv.IsNil() {
panic("value to scan must be non-nil pointer")
}
stopTheWorld("memsize scan")
defer startTheWorld()
ctx := newContext()
ctx.scan(invalidAddr, rv, false)
ctx.s.BitmapSize = ctx.seen.size()
ctx.s.BitmapUtilization = ctx.seen.utilization()
return *ctx.s
}
// Sizes is the result of a scan.
type Sizes struct {
Total uintptr
ByType map[reflect.Type]*TypeSize
// Internal stats (for debugging)
BitmapSize uintptr
BitmapUtilization float32
}
type TypeSize struct {
Total uintptr
Count uintptr
}
func newSizes() *Sizes {
return &Sizes{ByType: make(map[reflect.Type]*TypeSize)}
}
// Report returns a human-readable report.
func (s Sizes) Report() string {
type typLine struct {
name string
count uintptr
total uintptr
}
tab := []typLine{{"ALL", 0, s.Total}}
for _, typ := range s.ByType {
tab[0].count += typ.Count
}
maxname := 0
for typ, s := range s.ByType {
line := typLine{typ.String(), s.Count, s.Total}
tab = append(tab, line)
if len(line.name) > maxname {
maxname = len(line.name)
}
}
sort.Slice(tab, func(i, j int) bool { return tab[i].total > tab[j].total })
buf := new(bytes.Buffer)
w := tabwriter.NewWriter(buf, 0, 0, 0, ' ', tabwriter.AlignRight)
for _, line := range tab {
namespace := strings.Repeat(" ", maxname-len(line.name))
fmt.Fprintf(w, "%s%s\t %v\t %s\t\n", line.name, namespace, line.count, HumanSize(line.total))
}
w.Flush()
return buf.String()
}
// addValue is called during scan and adds the memory of given object.
func (s *Sizes) addValue(v reflect.Value, size uintptr) {
s.Total += size
rs := s.ByType[v.Type()]
if rs == nil {
rs = new(TypeSize)
s.ByType[v.Type()] = rs
}
rs.Total += size
rs.Count++
}
type context struct {
// We track previously scanned objects to prevent infinite loops
// when scanning cycles and to prevent counting objects more than once.
seen *bitmap
tc typCache
s *Sizes
}
func newContext() *context {
return &context{seen: newBitmap(), tc: make(typCache), s: newSizes()}
}
// scan walks all objects below v, determining their size. All scan* functions return the
// amount of 'extra' memory (e.g. slice data) that is referenced by the object.
func (c *context) scan(addr address, v reflect.Value, add bool) (extraSize uintptr) {
size := v.Type().Size()
var marked uintptr
if addr.valid() {
marked = c.seen.countRange(uintptr(addr), size)
if marked == size {
return 0 // Skip if we have already seen the whole object.
}
c.seen.markRange(uintptr(addr), size)
}
// fmt.Printf("%v: %v ⮑ (marked %d)\n", addr, v.Type(), marked)
if c.tc.needScan(v.Type()) {
extraSize = c.scanContent(addr, v)
}
// fmt.Printf("%v: %v %d (add %v, size %d, marked %d, extra %d)\n", addr, v.Type(), size+extraSize, add, v.Type().Size(), marked, extraSize)
if add {
size -= marked
size += extraSize
c.s.addValue(v, size)
}
return extraSize
}
func (c *context) scanContent(addr address, v reflect.Value) uintptr {
switch v.Kind() {
case reflect.Array:
return c.scanArray(addr, v)
case reflect.Chan:
return c.scanChan(v)
case reflect.Func:
// can't do anything here
return 0
case reflect.Interface:
return c.scanInterface(v)
case reflect.Map:
return c.scanMap(v)
case reflect.Ptr:
if !v.IsNil() {
c.scan(address(v.Pointer()), v.Elem(), true)
}
return 0
case reflect.Slice:
return c.scanSlice(v)
case reflect.String:
return uintptr(v.Len())
case reflect.Struct:
return c.scanStruct(addr, v)
default:
unhandledKind(v.Kind())
return 0
}
}
func (c *context) scanChan(v reflect.Value) uintptr {
etyp := v.Type().Elem()
extra := uintptr(0)
if c.tc.needScan(etyp) {
// Scan the channel buffer. This is unsafe but doesn't race because
// the world is stopped during scan.
hchan := unsafe.Pointer(v.Pointer())
for i := uint(0); i < uint(v.Cap()); i++ {
addr := chanbuf(hchan, i)
elem := reflect.NewAt(etyp, addr).Elem()
extra += c.scanContent(address(addr), elem)
}
}
return uintptr(v.Cap())*etyp.Size() + extra
}
func (c *context) scanStruct(base address, v reflect.Value) uintptr {
extra := uintptr(0)
for i := 0; i < v.NumField(); i++ {
f := v.Type().Field(i)
if c.tc.needScan(f.Type) {
addr := base.addOffset(f.Offset)
extra += c.scanContent(addr, v.Field(i))
}
}
return extra
}
func (c *context) scanArray(addr address, v reflect.Value) uintptr {
esize := v.Type().Elem().Size()
extra := uintptr(0)
for i := 0; i < v.Len(); i++ {
extra += c.scanContent(addr, v.Index(i))
addr = addr.addOffset(esize)
}
return extra
}
func (c *context) scanSlice(v reflect.Value) uintptr {
slice := v.Slice(0, v.Cap())
esize := slice.Type().Elem().Size()
base := slice.Pointer()
// Add size of the unscanned portion of the backing array to extra.
blen := uintptr(slice.Len()) * esize
marked := c.seen.countRange(base, blen)
extra := blen - marked
c.seen.markRange(uintptr(base), blen)
if c.tc.needScan(slice.Type().Elem()) {
// Elements may contain pointers, scan them individually.
addr := address(base)
for i := 0; i < slice.Len(); i++ {
extra += c.scanContent(addr, slice.Index(i))
addr = addr.addOffset(esize)
}
}
return extra
}
func (c *context) scanMap(v reflect.Value) uintptr {
var (
typ = v.Type()
len = uintptr(v.Len())
extra = uintptr(0)
)
if c.tc.needScan(typ.Key()) || c.tc.needScan(typ.Elem()) {
for _, k := range v.MapKeys() {
extra += c.scan(invalidAddr, k, false)
extra += c.scan(invalidAddr, v.MapIndex(k), false)
}
}
return len*typ.Key().Size() + len*typ.Elem().Size() + extra
}
func (c *context) scanInterface(v reflect.Value) uintptr {
elem := v.Elem()
if !elem.IsValid() {
return 0 // nil interface
}
c.scan(invalidAddr, elem, false)
if !c.tc.isPointer(elem.Type()) {
// Account for non-pointer size of the value.
return elem.Type().Size()
}
return 0
}
|
