warn issues about large block I/O performance for Linux older than 4.0.0 (#14524)

This PR simply adds a warning message when it detects older kernel
versions and warn's them about potential performance issues on this
kernel.

The issue can be seen only with parallel I/O across all drives
on denser setups such as 90 drives or 45 drives per server configurations.

internal/kernel/kernel_utsname_int8.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2015-2022 MinIO, Inc.
+//
+// This file is part of MinIO Object Storage stack
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+//
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+//go:build (linux && 386) || (linux && amd64) || (linux && arm64) || (linux && mips64) || (linux && mips)
+// +build linux,386 linux,amd64 linux,arm64 linux,mips64 linux,mips
+
+package kernel
+
+func utsnameStr(in []int8) string {
+	out := make([]byte, 0, len(in))
+	for i := 0; i < len(in); i++ {
+		if in[i] == 0x00 {
+			break
+		}
+		out = append(out, byte(in[i]))
+	}
+	return string(out)
+}