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mem: skip defer for performance #48

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merged 1 commit into from
Sep 4, 2016
Merged

mem: skip defer for performance #48

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21 changes: 15 additions & 6 deletions mem.go
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Original file line number Diff line number Diff line change
Expand Up @@ -167,22 +167,27 @@ func (m *Message) NumSegments() int64 {

// Segment returns the segment with the given ID.
func (m *Message) Segment(id SegmentID) (*Segment, error) {
m.mu.Lock()
defer m.mu.Unlock()
var seg *Segment
if isInt32Bit() && id > maxInt32 {
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nit: this case doesn't require the mutex

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You mean we can move m.mu.Lock() below this block correct?

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Yup.

return nil, errSegment32Bit
}
if seg := m.segment(id); seg != nil {
m.mu.Lock()
if seg = m.segment(id); seg != nil {
m.mu.Unlock()
return seg, nil
}
if int64(id) >= m.Arena.NumSegments() {
m.mu.Unlock()
return nil, errSegmentOutOfBounds
}
data, err := m.Arena.Data(id)
if err != nil {
m.mu.Unlock()
return nil, err
}
return m.setSegment(id, data), nil
seg = m.setSegment(id, data)
m.mu.Unlock()
return seg, nil
}

// segment returns the segment with the given ID.
Expand Down Expand Up @@ -230,19 +235,23 @@ func (m *Message) setSegment(id SegmentID, data []byte) *Segment {
// cap(seg.Data) - len(seg.Data) >= sz.
func (m *Message) allocSegment(sz Size) (*Segment, error) {
m.mu.Lock()
defer m.mu.Unlock()
var seg *Segment
if m.segs == nil && m.firstSeg.msg != nil {
m.segs = make(map[SegmentID]*Segment)
m.segs[0] = &m.firstSeg
}
id, data, err := m.Arena.Allocate(sz, m.segs)
if err != nil {
m.mu.Unlock()
return nil, err
}
if isInt32Bit() && id > maxInt32 {
m.mu.Unlock()
return nil, errSegment32Bit
}
return m.setSegment(id, data), nil
seg = m.setSegment(id, data)
m.mu.Unlock()
return seg, nil
}

// alloc allocates sz zero-filled bytes. It prefers using s, but may
Expand Down