perf(sn): reuse buffer for ReplicateRequest unmarshaling #808
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Codecov ReportAll modified and coverable lines are covered by tests ✅
Additional details and impacted files@@ Coverage Diff @@
## main #808 +/- ##
==========================================
+ Coverage 68.09% 68.44% +0.35%
==========================================
Files 182 182
Lines 17899 17903 +4
==========================================
+ Hits 12188 12254 +66
+ Misses 4941 4863 -78
- Partials 770 786 +16 ☔ View full report in Codecov by Sentry. |
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hungryjang
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Jun 10, 2024
proto/snpb/replicator_test.go
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| require.Equal(t, want2, got2) | ||
| }) | ||
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| t.Run("GrowLength", func(t *testing.T) { |
There was a problem hiding this comment.
We need to check whether unmarshal or grow was successful.
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Improve unmarshaling performance by reusing buffers for ReplicateRequest in the
backup replica.
The protobuf message `github.com/kakao/varlog/proto/snpb.(ReplicateRequest)` has
two slice fields—LLSN (`[]uint64`) and Data (`[][]byte`). The backup replica
receives replicated log entries from the primary replica via the gRPC service
`github.com/kakao/varlog/proto/snpb.(ReplicatorServer).Replicate`, which sends
`ReplicateRequest` messages.
Upon receiving a `ReplicateRequest`, the backup replica unmarshals the message,
which involves growing slices for fields such as LLSN and Data. This growth
causes copy overhead whenever the slice capacities need to expand.
To address this, we introduce a new method, `ResetReuse`, for reusing slices
instead of resetting them completely. The `ResetReuse` method shrinks the slice
lengths while preserving their capacities, thus avoiding the overhead of
reallocating memory.
Example implementation:
```go
type Message struct {
Buffer []byte
// Other fields
}
func (m *Message) Reset() {
*m = Message{}
}
func (m *Message) ResetReuse() {
s := m.Buffer[:0]
*m = Message{}
m.Buffer = s
}
```
Risks:
This approach has potential downsides. Since the heap space consumed by the
slices is not reclaimed, the storage node's memory consumption may increase.
Currently, there is no mechanism to shrink the heap usage.
Additionally, this PR changes the generated code. The protobuf compiler can
revert it, which is contrary to our intention. To catch this mistake, this PR
includes a unit test (github.com/kakao/varlog/proto/snpb.TestReplicateRequest)
to verify that the buffer backing the slices is reused.
Resolves: #795
See also: #806
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hungryjang
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Jul 29, 2024
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What this PR does
Improve unmarshaling performance by reusing buffers for ReplicateRequest in the
backup replica.
The protobuf message
github.com/kakao/varlog/proto/snpb.(ReplicateRequest)hastwo slice fields—LLSN (
[]uint64) and Data ([][]byte). The backup replicareceives replicated log entries from the primary replica via the gRPC service
github.com/kakao/varlog/proto/snpb.(ReplicatorServer).Replicate, which sendsReplicateRequestmessages.Upon receiving a
ReplicateRequest, the backup replica unmarshals the message,which involves growing slices for fields such as LLSN and Data. This growth
causes copy overhead whenever the slice capacities need to expand.
To address this, we introduce a new method,
ResetReuse, for reusing slicesinstead of resetting them completely. The
ResetReusemethod shrinks the slicelengths while preserving their capacities, thus avoiding the overhead of
reallocating memory.
Example implementation:
Risks:
This approach has potential downsides. Since the heap space consumed by the
slices is not reclaimed, the storage node's memory consumption may increase.
Currently, there is no mechanism to shrink the heap usage.
Additionally, this PR changes the generated code. The protobuf compiler can
revert it, which is contrary to our intention. To catch this mistake, this PR
includes a unit test (github.com/kakao/varlog/proto/snpb.TestReplicateRequest)
to verify that the buffer backing the slices is reused.
Which issue(s) this PR resolves
Resolves: #795
See also: #806