vold: add ro.vold.umsdirtyratio property

This allows control of what /proc/sys/vm/dirty_ratio is used when USB mounting.
Some platforms like the HTC Desire (bravo) get a _HUGE_ performance boost when
writing to the sdcard when USB mounting if this is set to 20 (which is the default)
on the HTC Desire.

This addresses this issue: http://code.google.com/p/cyanogenmod/issues/detail?id=2949

Basicly it makes it possible to undo or control the effect of this commit:
https://github.com/CyanogenMod/android_system_vold/commit/a28056b38275003895ff5d9576681aca01544822

Change-Id: I86b7bbd02695fb0c19f39448714a219257bf806f

1 files changed, 6 insertions, 2 deletions

diff --git a/VolumeManager.cpp b/VolumeManager.cpp
index 32a4707..d537ada 100644
--- a/VolumeManager.cpp
+++ b/VolumeManager.cpp
@@ -33,6 +33,7 @@
 #include <openssl/md5.h>
 
 #include <cutils/log.h>
+#include <cutils/properties.h>
 
 #include <sysutils/NetlinkEvent.h>
 
@@ -64,9 +65,12 @@ VolumeManager::VolumeManager() {
     mBroadcaster = NULL;
     mUmsSharingCount = 0;
     mSavedDirtyRatio = -1;
-    // set dirty ratio to 0 when UMS is active
-    mUmsDirtyRatio = 0;
     mVolManagerDisabled = 0;
+
+    // set dirty ratio to ro.vold.umsdirtyratio (default 0) when UMS is active
+    char dirtyratio[PROPERTY_VALUE_MAX];
+    property_get("ro.vold.umsdirtyratio", dirtyratio, "0");
+    mUmsDirtyRatio = atoi(dirtyratio);
 }
 
 VolumeManager::~VolumeManager() {