message: Fix reuse of first segment #556
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This fixes the Message's Reset() call to allow reuse of the first segment. Prior to this fix, the first segment was discarded after the first Reset call, effectively causing a new segment to be initialized on every Reset call. By reusing the first segment, the number of heap allocations is reduced and therefore performance is increased in use cases where the message object is reused. The fix involved associtating the segment to the message and fixing checks to ensure the data of the segment is re-allocated after the reset. A benchmark is included to show the current performance of this.
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Test failures seems unrelated. Re-running. Thank you for submitting this -- I am currently traveling, but will track this as closely as possible. |
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lthibault
requested changes
Jun 1, 2024
| @@ -100,6 +101,9 @@ func (m *Message) Release() { | |||
| func (m *Message) Reset(arena Arena) (first *Segment, err error) { | |||
| m.capTable.Reset() | |||
| for k := range m.segs { | |||
| if k == 0 && m.segs[k] == &m.firstSeg { | |||
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A comment might be helpful here. Something along the lines of:
// optimization: keep the first segment so that the re-used Message does not have to
// allocate a new one.| @@ -442,7 +447,7 @@ func alloc(s *Segment, sz Size) (*Segment, address, error) { | |||
| var err error | |||
| s, err = s.msg.allocSegment(sz) | |||
| if err != nil { | |||
| return nil, 0, err | |||
| return nil, 0, fmt.Errorf("allocSegment failed: %v", err) | |||
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We previously purged fmt form the code-base in order to avoid using reflection, which helps keep binary sizes small. I know it's a bit awkward, but can we replace this with errors.New("allocSegment failed: " + err.Error())?
| @@ -15,6 +15,8 @@ type SegmentID uint32 | |||
| // It is part of a Message, which can contain other segments that | |||
| // reference each other. | |||
| type Segment struct { | |||
| // msg associated with this segment. A Message instance m maintains the | |||
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This fixes the Message's Reset() call to allow reuse of the first segment.
Prior to this fix, the first segment was discarded after the first Reset call, effectively causing a new segment to be initialized on every Reset call.
By reusing the first segment, the number of heap allocations is reduced and therefore performance is increased in use cases where the message object is reused.
The fix involved associtating the segment to the message and fixing checks to ensure the data of the segment is re-allocated after the reset.
A benchmark is included to show the current performance of this.
Part of #554