logging: avoid unnecessary printfs

Don't spend CPU cycles formatting a bunch of strings if we're
just going to throw them away later. Maybe make booting faster.

Change-Id: I4d8eb99fb3fa873ca91cf776933d0ad01988abf5

init/log.cpp

@@ -27,6 +27,8 @@
 static void init_klog_vwrite(int level, const char* fmt, va_list ap) {
     static const char* tag = basename(getprogname());
 
+    if (level > klog_get_level()) return;
+
     // The kernel's printk buffer is only 1024 bytes.
     // TODO: should we automatically break up long lines into multiple lines?
     // Or we could log but with something like "..." at the end?

libcutils/klog.c

@@ -62,6 +62,7 @@ void klog_writev(int level, const struct iovec* iov, int iov_count) {
 }
 
 void klog_write(int level, const char* fmt, ...) {
+    if (level > klog_level) return;
     char buf[LOG_BUF_MAX];
     va_list ap;
     va_start(ap, fmt);