avoid using 10MiB EC buffers in maxAPI calculations (#19665)

max requests per node is more conservative in its value
causing premature serialization of the calls, avoid it
for newer deployments.

cmd/config-current.go

@@ -575,7 +575,7 @@ func applyDynamicConfigForSubSys(ctx context.Context, objAPI ObjectLayer, s conf
 			configLogIf(ctx, fmt.Errorf("Invalid api configuration: %w", err))
 		}
 
-		globalAPIConfig.init(apiConfig, setDriveCounts)
+		globalAPIConfig.init(apiConfig, setDriveCounts, objAPI.Legacy())
 		autoGenerateRootCredentials() // Generate the KMS root credentials here since we don't know whether API root access is disabled until now.
 		setRemoteInstanceTransport(NewHTTPTransportWithTimeout(apiConfig.RemoteTransportDeadline))
 	case config.CompressionSubSys:

cmd/erasure-server-pool.go

@@ -1,4 +1,4 @@
-// Copyright (c) 2015-2021 MinIO, Inc.
+// Copyright (c) 2015-2024 MinIO, Inc.
 //
 // This file is part of MinIO Object Storage stack
 //
@@ -644,6 +644,15 @@ func (z *erasureServerPools) Shutdown(ctx context.Context) error {
 	return nil
 }
 
+// Legacy returns 'true' if distribution algo is CRCMOD
+func (z *erasureServerPools) Legacy() (ok bool) {
+	ok = true
+	for _, set := range z.serverPools {
+		ok = ok && set.Legacy()
+	}
+	return ok
+}
+
 func (z *erasureServerPools) BackendInfo() (b madmin.BackendInfo) {
 	b.Type = madmin.Erasure
 

cmd/erasure-sets.go

@@ -194,6 +194,11 @@ func findDiskIndex(refFormat, format *formatErasureV3) (int, int, error) {
 	return -1, -1, fmt.Errorf("DriveID: %s not found", format.Erasure.This)
 }
 
+// Legacy returns 'true' if distribution algo is CRCMOD
+func (s *erasureSets) Legacy() (ok bool) {
+	return s.distributionAlgo == formatErasureVersionV2DistributionAlgoV1
+}
+
 // connectDisks - attempt to connect all the endpoints, loads format
 // and re-arranges the disks in proper position.
 func (s *erasureSets) connectDisks() {

cmd/handler-api.go

@@ -22,6 +22,7 @@ import (
 	"net/http"
 	"os"
 	"runtime"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -43,8 +44,6 @@ type apiConfig struct {
 	clusterDeadline       time.Duration
 	listQuorum            string
 	corsAllowOrigins      []string
-	// total drives per erasure set across pools.
-	totalDriveCount       int
 	replicationPriority   string
 	replicationMaxWorkers int
 	transitionWorkers     int
@@ -110,7 +109,7 @@ func availableMemory() (available uint64) {
 	return
 }
 
-func (t *apiConfig) init(cfg api.Config, setDriveCounts []int) {
+func (t *apiConfig) init(cfg api.Config, setDriveCounts []int, legacy bool) {
 	t.mu.Lock()
 	defer t.mu.Unlock()
 
@@ -125,27 +124,24 @@ func (t *apiConfig) init(cfg api.Config, setDriveCounts []int) {
 	}
 	t.corsAllowOrigins = corsAllowOrigin
 
-	maxSetDrives := 0
-	for _, setDriveCount := range setDriveCounts {
-		t.totalDriveCount += setDriveCount
-		if setDriveCount > maxSetDrives {
-			maxSetDrives = setDriveCount
-		}
-	}
-
 	var apiRequestsMaxPerNode int
 	if cfg.RequestsMax <= 0 {
+		maxSetDrives := slices.Max(setDriveCounts)
+
 		// Returns 75% of max memory allowed
 		maxMem := availableMemory()
 
 		// max requests per node is calculated as
 		// total_ram / ram_per_request
-		// ram_per_request is (2MiB+128KiB) * driveCount \
-		//    + 2 * 10MiB (default erasure block size v1) + 2 * 1MiB (default erasure block size v2)
 		blockSize := xioutil.LargeBlock + xioutil.SmallBlock
+		if legacy {
+			// ram_per_request is (1MiB+32KiB) * driveCount \
+			//    + 2 * 10MiB (default erasure block size v1) + 2 * 1MiB (default erasure block size v2)
 			apiRequestsMaxPerNode = int(maxMem / uint64(maxSetDrives*blockSize+int(blockSizeV1*2+blockSizeV2*2)))
-		if globalIsDistErasure {
-			logger.Info("Automatically configured API requests per node based on available memory on the system: %d", apiRequestsMaxPerNode)
+		} else {
+			// ram_per_request is (1MiB+32KiB) * driveCount \
+			//    + 2 * 1MiB (default erasure block size v2)
+			apiRequestsMaxPerNode = int(maxMem / uint64(maxSetDrives*blockSize+int(blockSizeV2*2)))
 		}
 	} else {
 		apiRequestsMaxPerNode = cfg.RequestsMax
@@ -154,6 +150,10 @@ func (t *apiConfig) init(cfg api.Config, setDriveCounts []int) {
 		}
 	}
 
+	if globalIsDistErasure {
+		logger.Info("Configured max API requests per node based on available memory: %d", apiRequestsMaxPerNode)
+	}
+
 	if cap(t.requestsPool) != apiRequestsMaxPerNode {
 		// Only replace if needed.
 		// Existing requests will use the previous limit,

cmd/object-api-interface.go

@@ -244,6 +244,7 @@ type ObjectLayer interface {
 	Shutdown(context.Context) error
 	NSScanner(ctx context.Context, updates chan<- DataUsageInfo, wantCycle uint32, scanMode madmin.HealScanMode) error
 	BackendInfo() madmin.BackendInfo
+	Legacy() bool // Only returns true for deployments which use CRCMOD as its object distribution algorithm.
 	StorageInfo(ctx context.Context, metrics bool) StorageInfo
 	LocalStorageInfo(ctx context.Context, metrics bool) StorageInfo