kv: protect Replica's lastToReplica and lastFromReplica fields with raftMu#74355
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craig[bot] merged 1 commit intocockroachdb:masterfrom Jan 10, 2022
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Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status:complete! 0 of 0 LGTMs obtained (waiting on @nvanbenschoten)
pkg/kv/kvserver/replica_raft.go, line 1286 at r1 (raw file):
// sendRaftMessage sends a Raft message. func (r *Replica) sendRaftMessage(ctx context.Context, msg raftpb.Message) {
sendRaftMessageRaftMuLocked?
pkg/kv/kvserver/replica_raft_quiesce.go, line 401 at r1 (raw file):
} func (r *Replica) quiesceAndNotifyLocked(
RaftMuLocked?
…aftMu This commit moves the Replica's lastToReplica and lastFromReplica from under the `Replica.mu` mutex to the `Replica.raftMu` mutex. These are strictly Raft-specific pieces of state, so we don't need fine-grained locking around them. As a reward, we don't need to grab the `Replica.mu` exclusively (or at all) when setting the fields in `Store.withReplicaForRequest`. The locking in `setLastReplicaDescriptors` showed up in a mutex profile under a write-heavy workload. It was responsible for **3.44%** of mutex wait time. Grabbing the mutex was probably also slowing down request processing, as the exclusive lock acquisition had to wait for read locks to be dropped.
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nvb
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Jan 10, 2022
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TFTR!
Reviewable status:
pkg/kv/kvserver/replica_raft.go, line 1286 at r1 (raw file):
Previously, tbg (Tobias Grieger) wrote…
sendRaftMessageRaftMuLocked?
Done.
pkg/kv/kvserver/replica_raft_quiesce.go, line 401 at r1 (raw file):
Previously, tbg (Tobias Grieger) wrote…
RaftMuLocked?
Done.
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This commit moves the Replica's lastToReplica and lastFromReplica from
under the
Replica.mumutex to theReplica.raftMumutex. These arestrictly Raft-specific pieces of state, so we don't need fine-grained
locking around them. As a reward, we don't need to grab the
Replica.muexclusively (or at all) when setting the fields in
Store.withReplicaForRequest.The locking in
setLastReplicaDescriptorsshowed up in a mutex profileunder a write-heavy workload. It was responsible for 3.44% of mutex
wait time. Grabbing the mutex was probably also slowing down request
processing, as the exclusive lock acquisition had to wait for read locks
to be dropped.