sreadahead: Add a patch to set the app to io-idle running status.

This patch sets the sreadahead to io-idle stauts when it is running,
so that sreadahead will not preempt IO with other apps.

meta-moblin/packages/sreadahead/sreadahead-0.02/set_to_idle.patch

@@ -0,0 +1,39 @@
+diff -Naurp sreadahead-0.02/readahead.c sreadahead-0.02-nice/readahead.c
+--- sreadahead-0.02/readahead.c	2008-11-06 00:57:17.000000000 -0500
++++ sreadahead-0.02-nice/readahead.c	2008-11-06 02:28:29.000000000 -0500
+@@ -26,7 +26,18 @@
+ #include <errno.h>
+ 
+ #include "readahead.h"
++#include <sys/syscall.h>
+ 
++# if defined(__i386__)
++#  define __NR_ioprio_set	289
++# elif defined(__x86_64__)
++#  define __NR_ioprio_set	251
++# else
++#  error "Unsupported arch"
++# endif
++
++#define IOPRIO_WHO_PROCESS	1
++#define IOPRIO_CLASS_SHIFT	13
+ #define MAXR 1024
+ static struct readahead files[MAXR];
+ static unsigned int total_files = 0;
+@@ -68,7 +79,15 @@ void *one_thread(void *ptr)
+ 
+ int main(int argc, char **argv)
+ {
+-	FILE *file = fopen("/etc/readahead.packed", "r");
++	int iopriority = 7; /* hard code for idle */
++	int iopriority_class = 3; /* 3 stands for idle */
++	int pid = 0;
++	FILE *file;
++
++	if (syscall(__NR_ioprio_set, IOPRIO_WHO_PROCESS, pid, iopriority | iopriority_class << IOPRIO_CLASS_SHIFT) == -1)
++		perror("Can not set priority to idle class");
++
++	file = fopen("/etc/readahead.packed", "r");
+ 	if (!file) {
+ 		perror("Couldnt open /etc/readahead.packed");
+ 		return -errno;

meta-moblin/packages/sreadahead/sreadahead_0.02.bb

@@ -9,6 +9,7 @@ inherit update-rc.d
 SRC_URI = "http://www.moblin.org/sites/all/files/sreadahead-${PV}.tar.gz \
 	  file://sreadahead-0.02-make.patch;patch=1 \
 	  file://readahead_c.patch;patch=1 \
+	  file://set_to_idle.patch;patch=1 \
 	  file://sreadahead-generate.sh \
 	  file://sreadahead.sh"