cherry pick pingcap#30428 to release-5.2

Signed-off-by: ti-srebot <ti-srebot@pingcap.com>

br/pkg/lightning/backend/local/local.go

@@ -91,7 +91,8 @@ const (
 	gRPCBackOffMaxDelay  = 10 * time.Minute
 
 	// See: https://github.com/tikv/tikv/blob/e030a0aae9622f3774df89c62f21b2171a72a69e/etc/config-template.toml#L360
-	regionMaxKeyCount      = 1_440_000
+	// lower the max-key-count to avoid tikv trigger region auto split
+	regionMaxKeyCount      = 1_280_000
 	defaultRegionSplitSize = 96 * units.MiB
 
 	propRangeIndex = "tikv.range_index"
@@ -1499,7 +1500,16 @@ func (local *local) WriteToTiKV(
 	size := int64(0)
 	totalCount := int64(0)
 	firstLoop := true
+<<<<<<< HEAD
 	regionMaxSize := local.regionSplitSize * 4 / 3
+=======
+	// if region-split-size <= 96MiB, we bump the threshold a bit to avoid too many retry split
+	// because the range-properties is not 100% accurate
+	regionMaxSize := regionSplitSize
+	if regionSplitSize <= defaultRegionSplitSize {
+		regionMaxSize = regionSplitSize * 4 / 3
+	}
+>>>>>>> 92207005e... lightning: optimize region split check logic (#30428)
 
 	for iter.First(); iter.Valid(); iter.Next() {
 		size += int64(len(iter.Key()) + len(iter.Value()))

br/pkg/lightning/restore/table_restore.go

@@ -956,8 +956,8 @@ func estimateCompactionThreshold(cp *checkpoints.TableCheckpoint, factor int64)
 	threshold := totalRawFileSize / 512
 	threshold = utils.NextPowerOfTwo(threshold)
 	if threshold < compactionLowerThreshold {
-		// disable compaction if threshold is smaller than lower bound
-		threshold = 0
+		// too may small SST files will cause inaccuracy of region range estimation,
+		threshold = compactionLowerThreshold
 	} else if threshold > compactionUpperThreshold {
 		threshold = compactionUpperThreshold
 	}