core: change scoreV2 to adapt the higher disk capacity and amp . (#4837)

server/core/store.go

@@ -359,7 +359,7 @@ func (s *StoreInfo) regionScoreV2(delta int64, lowSpaceRatio float64) float64 {
 	var (
 		K, M float64 = 1, 256 // Experience value to control the weight of the available influence on score
 		F    float64 = 50     // Experience value to prevent some nodes from running out of disk space prematurely.
-		B            = 1e7
+		B            = 1e10
 	)
 	F = math.Max(F, C*(1-lowSpaceRatio))
 	var score float64

server/core/store_test.go

@@ -142,8 +142,8 @@ func (s *testStoreSuite) TestLowSpaceScoreV2(c *C) {
 		small:  NewStoreInfoWithAvailable(2, 10*gb, 100*gb, 1.4),
 	}, {
 		// store1 and store2 has same available ratio less than 0.2
-		bigger: NewStoreInfoWithAvailable(1, 10*gb, 1000*gb, 1.4),
-		small:  NewStoreInfoWithAvailable(2, 1*gb, 100*gb, 1.4),
+		bigger: NewStoreInfoWithAvailable(1, 20*gb, 1000*gb, 1.4),
+		small:  NewStoreInfoWithAvailable(2, 10*gb, 500*gb, 1.4),
 	}, {
 		// store1 and store2 has same available ratio
 		// but the store1 ratio less than store2 ((50-10)/50=0.8<(200-100)/200=0.5)
@@ -164,6 +164,10 @@ func (s *testStoreSuite) TestLowSpaceScoreV2(c *C) {
 		// but store1 has higher amp, so store1(60g) has more regionSize (40g)
 		bigger: NewStoreInfoWithAvailable(1, 80*gb, 100*gb, 3),
 		small:  NewStoreInfoWithAvailable(2, 60*gb, 100*gb, 1),
+	}, {
+		// store1's capacity is less than store2's capacity, but store2 has more available space,
+		bigger: NewStoreInfoWithAvailable(1, 2*gb, 100*gb, 3),
+		small:  NewStoreInfoWithAvailable(2, 100*gb, 10*1000*gb, 3),
 	}}
 	for _, v := range testdata {
 		score1 := v.bigger.regionScoreV2(0, 0.8)

server/core/test_util.go

@@ -84,7 +84,7 @@ func NewTestRegionInfo(start, end []byte) *RegionInfo {
 	}}
 }
 
-// NewStoreInfoWithAvailable is create with available and capacity
+// NewStoreInfoWithAvailable is created with available and capacity
 func NewStoreInfoWithAvailable(id, available, capacity uint64, amp float64) *StoreInfo {
 	stats := &pdpb.StoreStats{}
 	stats.Capacity = capacity