From 54356650e16162bcb53dff5f078afc2931a0edce Mon Sep 17 00:00:00 2001
From: shirou <shirou.faw@gmail.com>
Date: Sun, 27 Aug 2023 09:03:20 +0000
Subject: [PATCH] [common][linux]: improve readlines performance.

---
 internal/common/common.go       | 9 +++++++--
 internal/common/common_linux.go | 3 ++-
 process/process_linux.go        | 5 ++++-
 process/process_test.go         | 6 ++++++
 4 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/internal/common/common.go b/internal/common/common.go
index 9bfece362..5fcd68b79 100644
--- a/internal/common/common.go
+++ b/internal/common/common.go
@@ -109,9 +109,14 @@ func ReadFile(filename string) (string, error) {
 }
 
 // ReadLines reads contents from a file and splits them by new lines.
-// A convenience wrapper to ReadLinesOffsetN(filename, 0, -1).
+// Please do not use this function on Windows platform.
 func ReadLines(filename string) ([]string, error) {
-	return ReadLinesOffsetN(filename, 0, -1)
+	bytes, err := os.ReadFile(filename)
+	if err != nil {
+		return []string{""}, err
+	}
+	lines := strings.Split(strings.Trim(string(bytes), "\n"), "\n")
+	return lines, nil
 }
 
 // ReadLinesOffsetN reads contents from file and splits them by new line.
diff --git a/internal/common/common_linux.go b/internal/common/common_linux.go
index b58edbeb0..770d28e6f 100644
--- a/internal/common/common_linux.go
+++ b/internal/common/common_linux.go
@@ -89,7 +89,8 @@ func BootTimeWithContext(ctx context.Context) (uint64, error) {
 	}
 
 	if statFile == "stat" {
-		for _, line := range lines {
+		for i := len(lines) - 1; i > 0; i-- {
+			line := lines[i]
 			if strings.HasPrefix(line, "btime") {
 				f := strings.Fields(line)
 				if len(f) != 2 {
diff --git a/process/process_linux.go b/process/process_linux.go
index 37cb7ca44..57a28a06f 100644
--- a/process/process_linux.go
+++ b/process/process_linux.go
@@ -1072,7 +1072,10 @@ func (p *Process) fillFromTIDStatWithContext(ctx context.Context, tid int32) (ui
 		Iowait: iotime / float64(clockTicks),
 	}
 
-	bootTime, _ := common.BootTimeWithContext(ctx)
+	bootTime, err := common.BootTimeWithContext(ctx)
+	if err != nil {
+		return 0, 0, nil, 0, 0, 0, nil, err
+	}
 	t, err := strconv.ParseUint(fields[22], 10, 64)
 	if err != nil {
 		return 0, 0, nil, 0, 0, 0, nil, err
diff --git a/process/process_test.go b/process/process_test.go
index 9281c93c3..21aba5718 100644
--- a/process/process_test.go
+++ b/process/process_test.go
@@ -862,3 +862,9 @@ func BenchmarkProcessPpid(b *testing.B) {
 		p.Ppid()
 	}
 }
+
+func BenchmarkProcesses(b *testing.B) {
+	for i := 0; i < b.N; i++ {
+		Processes()
+	}
+}