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logstore: pool MVCCStats to avoid hot path allocs #113742

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merged 1 commit into from
Nov 3, 2023
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logstore: pool MVCCStats to avoid hot path allocs #113742

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29 changes: 21 additions & 8 deletions pkg/kv/kvserver/logstore/logstore.go
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Original file line number Diff line number Diff line change
Expand Up @@ -360,8 +360,13 @@ var nonBlockingSyncWaiterCallbackPool = sync.Pool{
New: func() interface{} { return new(nonBlockingSyncWaiterCallback) },
}

var valPool = sync.Pool{
New: func() interface{} { return &roachpb.Value{} },
var logAppendPool = sync.Pool{
New: func() interface{} {
return new(struct {
roachpb.Value
enginepb.MVCCStats
})
Comment on lines +365 to +368
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nit: may as well give this type a name, but don't really care either way.

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@pav-kv pav-kv Nov 3, 2023 •
edited
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Meh, I think that's one of the cases where it's somewhat beneficial to not introduce a type explicitly (so that there is zero encouragement to use it elsewhere). There is exactly one caller/user of this type, and it's tied to the pool, and the pool is tied to a single function (also a reason why I renamed the pool after the function's name).

},
}

// logAppend adds the given entries to the raft log. Takes the previous log
Expand All @@ -382,13 +387,21 @@ func logAppend(
if len(entries) == 0 {
return prev, nil
}
var diff enginepb.MVCCStats
opts := storage.MVCCWriteOptions{
Stats: &diff,
}
value := valPool.Get().(*roachpb.Value)

// NB: the Value and MVCCStats lifetime is this function, so we coalesce their
// allocation into the same pool.
// TODO(pavelkalinnikov): figure out why they escape into the heap, and find a
// way to avoid the pool.
v := logAppendPool.Get().(*struct {
roachpb.Value
enginepb.MVCCStats
})
defer logAppendPool.Put(v)
value, diff := &v.Value, &v.MVCCStats
value.RawBytes = value.RawBytes[:0]
defer valPool.Put(value)
diff.Reset()

opts := storage.MVCCWriteOptions{Stats: diff}
for i := range entries {
ent := &entries[i]
key := keys.RaftLogKeyFromPrefix(raftLogPrefix, kvpb.RaftIndex(ent.Index))
Expand Down