mining lookback is effectively a constant - make it so

chain/actors/policy/policy.go

@@ -187,6 +187,7 @@ func GetWinningPoStSectorSetLookback(nwVer network.Version) abi.ChainEpoch {
 		return 10
 	}
 
+	// NOTE: if this ever changes, adjust it in a (*Miner).mineOne() logline as well
 	return ChainFinality
 }
 

miner/miner.go

@@ -432,24 +432,12 @@ func (m *Miner) mineOne(ctx context.Context, base *MiningBase) (*types.BlockMsg,
 
 	// always write out a log from this point out
 	var winner *types.ElectionProof
-	lookBack := make(chan int64)
-
-	// figure this out in the background, instead of slowing down the main loop
-	go func() {
-		lb := int64(-1)
-		if netVer, err := m.api.StateNetworkVersion(ctx, base.TipSet.Key()); err == nil {
-			lb = int64(policy.GetWinningPoStSectorSetLookback(netVer))
-		}
-		lookBack <- lb
-	}()
-
 	defer func() {
-
 		log.Infow(
 			"completed mineOne",
 			"forRound", int64(round),
 			"baseEpoch", int64(base.TipSet.Height()),
-			"lookbackEpochs", <-lookBack,
+			"lookbackEpochs", int64(policy.ChainFinality), // hardcoded as it is unlikely to change again: https://github.com/filecoin-project/lotus/blob/v1.8.0/chain/actors/policy/policy.go#L180-L186
 			"networkPowerAtLookback", mbi.NetworkPower.String(),
 			"minerPowerAtLookback", mbi.MinerPower.String(),
 			"isEligible", mbi.EligibleForMining,