Lower the priority of the threads in logd/logcat.

sched_batch implies only a penalty to latency in scheduling, but
does not imply that the process will be given less cpu time. Increase
the nice level to 10 to prioritize it below ui threads.

Bug: 21696721
Change-Id: I075af059dc755402f7df9b0d7a66cca921ff04b2

logcat/logcat.cpp

@@ -14,6 +14,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <sys/cdefs.h>
+#include <sys/resource.h>
 #include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/types.h>
@@ -33,6 +34,7 @@
 #include <log/logd.h>
 #include <log/logger.h>
 #include <log/logprint.h>
+#include <utils/threads.h>
 
 #define DEFAULT_MAX_ROTATED_LOGS 4
 
@@ -221,6 +223,10 @@ static void setupOutput()
             fprintf(stderr, "failed to set to batch scheduler\n");
         }
 
+        if (setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND) < 0) {
+            fprintf(stderr, "failed set to priority\n");
+        }
+
         g_outFD = openLogFile (g_outputFileName);
 
         if (g_outFD < 0) {

logd/main.cpp

@@ -27,6 +27,7 @@
 #include <sys/capability.h>
 #include <sys/klog.h>
 #include <sys/prctl.h>
+#include <sys/resource.h>
 #include <sys/stat.h>
 #include <sys/types.h>
 #include <syslog.h>
@@ -37,6 +38,7 @@
 #include <cutils/sockets.h>
 #include <log/event_tag_map.h>
 #include <private/android_filesystem_config.h>
+#include <utils/threads.h>
 
 #include "CommandListener.h"
 #include "LogBuffer.h"
@@ -91,6 +93,10 @@ static int drop_privs() {
         return -1;
     }
 
+    if (setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND) < 0) {
+        return -1;
+    }
+
     if (prctl(PR_SET_KEEPCAPS, 1) < 0) {
         return -1;
     }
@@ -156,6 +162,7 @@ static LogBuffer *logBuf = NULL;
 static void *reinit_thread_start(void * /*obj*/) {
     prctl(PR_SET_NAME, "logd.daemon");
     set_sched_policy(0, SP_BACKGROUND);
+    setpriority(PRIO_PROCESS, 0, ANDROID_PRIORITY_BACKGROUND);
 
     setgid(AID_SYSTEM);
     setuid(AID_SYSTEM);