From 87443af49e843745855e64cc193bd82c610b9abb Mon Sep 17 00:00:00 2001
From: Klaus Post <klauspost@gmail.com>
Date: Wed, 27 Nov 2019 06:40:13 -0800
Subject: [PATCH] Cache Windows mount point info (#8572)

It seems like every upload creates a new StorageInfo object.

This makes it very sensitive to slow code paths.

A particular slow function is `IsLikelyMountPoint` on Windows since `windows.GetVolumePathName` is slow.

We cache the result of this operation.

Before:

```
Operation: PUT - Concurrency: 12
* Average: 70.46 MB/s, 70.46 obj/s, 70.46 ops ended/s (59.58s)

Aggregated, split into 59 x 1s time segments:
* Fastest: 77.67 MB/s, 77.67 obj/s, 79.00 ops ended/s (1s)
* 50% Median: 70.84 MB/s, 70.84 obj/s, 70.00 ops ended/s (1s)
* Slowest: 61.51 MB/s, 61.51 obj/s, 61.00 ops ended/s (1s)
```

After:
```
Operation: PUT - Concurrency: 12
* Average: 166.80 MB/s, 166.80 obj/s, 166.74 ops ended/s (59.8s)

Aggregated, split into 59 x 1s time segments:
* Fastest: 183.83 MB/s, 183.83 obj/s, 186.00 ops ended/s (1s)
* 50% Median: 167.47 MB/s, 167.47 obj/s, 166.00 ops ended/s (1s)
* Slowest: 139.30 MB/s, 139.30 obj/s, 141.00 ops ended/s (1s)
```
---
 pkg/mountinfo/mountinfo_windows.go | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/pkg/mountinfo/mountinfo_windows.go b/pkg/mountinfo/mountinfo_windows.go
index 961a4f4d6..dc8ef340b 100644
--- a/pkg/mountinfo/mountinfo_windows.go
+++ b/pkg/mountinfo/mountinfo_windows.go
@@ -19,6 +19,9 @@
 package mountinfo
 
 import (
+	"path/filepath"
+	"sync"
+
 	"golang.org/x/sys/windows"
 )
 
@@ -28,12 +31,20 @@ func CheckCrossDevice(paths []string) error {
 	return nil
 }
 
+// mountPointCache contains results of IsLikelyMountPoint
+var mountPointCache sync.Map
+
 // IsLikelyMountPoint determines if a directory is a mountpoint.
 func IsLikelyMountPoint(path string) bool {
+	path = filepath.Dir(path)
+	if v, ok := mountPointCache.Load(path); ok {
+		return v.(bool)
+	}
 	wpath, _ := windows.UTF16PtrFromString(path)
 	wvolume := make([]uint16, len(path)+1)
 
 	if err := windows.GetVolumePathName(wpath, &wvolume[0], uint32(len(wvolume))); err != nil {
+		mountPointCache.Store(path, false)
 		return false
 	}
 
@@ -42,7 +53,9 @@ func IsLikelyMountPoint(path string) bool {
 		// Recognize "fixed", "removable", "remote" and "ramdisk" drives as proper drives
 		// which can be treated as an actual mount-point, rest can be ignored.
 		// https://docs.microsoft.com/en-us/windows/desktop/api/fileapi/nf-fileapi-getdrivetypew
+		mountPointCache.Store(path, true)
 		return true
 	}
+	mountPointCache.Store(path, false)
 	return false
 }