enlarge preallocated space. sync file system on exit.

src/libos/src/entry.rs

@@ -78,5 +78,11 @@ fn do_boot(path_str: &str, argv: &Vec<CString>) -> Result<(), Error> {
 // TODO: make sure do_run() cannot be called after do_boot()
 fn do_run() -> Result<i32, Error> {
     let exit_status = process::run_task()?;
+
+    // sync file system
+    // TODO: only sync when all processes exit
+    use rcore_fs::vfs::FileSystem;
+    crate::fs::ROOT_INODE.fs().sync()?;
+
     Ok(exit_status)
 }

src/libos/src/vm/vm_space_prealloced.c

@@ -1,6 +1,6 @@
 #include <stddef.h>
 
-#define DATA_SPACE_SIZE (32*1024*1024)
+#define DATA_SPACE_SIZE (96*1024*1024)
 
 static char __prealloced_data_space[DATA_SPACE_SIZE]
     __attribute__ ((