Added code for custom file prefetching

fs/nfs/Makefile

@@ -7,7 +7,7 @@ obj-$(CONFIG_NFS_FS) += nfs.o
 CFLAGS_nfstrace.o += -I$(src)
 nfs-y 			:= client.o dir.o file.o getroot.o inode.o super.o \
 			   direct.o pagelist.o read.o symlink.o unlink.o \
-			   write.o namespace.o mount_clnt.o nfstrace.o
+			   write.o namespace.o mount_clnt.o nfstrace.o prefetch.o
 nfs-$(CONFIG_ROOT_NFS)	+= nfsroot.o
 nfs-$(CONFIG_SYSCTL)	+= sysctl.o
 nfs-$(CONFIG_NFS_FSCACHE) += fscache.o fscache-index.o

fs/nfs/nfs4_fs.h

@@ -473,6 +473,7 @@ extern char nfs4_client_id_uniquifier[NFS4_CLIENT_ID_UNIQ_LEN];
 /* nfs4sysctl.c */
 #ifdef CONFIG_SYSCTL
 int nfs4_register_sysctl(void);
+int prefetch_register_sysctl(void);
 void nfs4_unregister_sysctl(void);
 #else
 static inline int nfs4_register_sysctl(void)

fs/nfs/nfs4super.c

@@ -334,6 +334,10 @@ static int __init init_nfs_v4(void)
 	if (err)
 		goto out2;
 
+	err = prefetch_register_sysctl();
+	if (err)
+		goto out2;
+
 	register_nfs_version(&nfs_v4);
 	return 0;
 out2:

fs/nfs/prefetch.c

@@ -0,0 +1,53 @@
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/nfs_fs.h>
+#include <linux/nfs_fs_sb.h>
+#include <linux/in6.h>
+#include <linux/seq_file.h>
+#include <linux/slab.h>
+#include <linux/sysctl.h>
+
+#include "internal.h"
+#include "iostat.h"
+#include "fscache.h"
+
+
+static int global_var;
+static int min_val = 0;
+static int max_val = 5;
+
+static struct ctl_table prefetch_child_table[] = {
+{
+	//.ctl_name = CTL_UNNUMBERED,
+	.procname = "prefetch",
+	.maxlen = sizeof(int),
+	.mode = 0644,
+	.data = &global_var,
+	.proc_handler = &proc_dointvec_minmax,
+	.extra1 = &min_val,
+	.extra2 = &max_val,
+},
+{}
+};
+
+static struct ctl_table prefetch_parent_table[] = {
+{
+	//.ctl_name = CTL_KERN,
+	.procname = "kernel",
+	.mode = 0555,
+	.child = prefetch_child_table,
+},
+{}
+};
+
+int prefetch_register_sysctl(void)
+{
+	/* register the above sysctl */
+	if (!register_sysctl_table(prefetch_parent_table)) {
+		printk(KERN_ALERT "Error: Failed to register sample_parent_table\n");
+		return -EFAULT;
+	}
+	return 0;
+}

mm/filemap.c

@@ -1760,6 +1760,12 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 	loff_t *ppos = &iocb->ki_pos;
 	loff_t pos = *ppos;
 
+	if (file->f_path.dentry) {
+		if (strstr(file->f_path.dentry->d_name.name, ".tar")) {
+			printk("RDTSC=%llu\n", (unsigned long long)rdtsc());
+		}
+	}
+
 	if (iocb->ki_flags & IOCB_DIRECT) {
 		struct address_space *mapping = file->f_mapping;
 		struct inode *inode = mapping->host;

mm/page_alloc.c

@@ -68,6 +68,9 @@
 #include <asm/div64.h>
 #include "internal.h"
 
+unsigned long lt = 0;
+unsigned long st = 0;
+
 /* prevent >1 _updater_ of zone percpu pageset ->high and ->batch fields */
 static DEFINE_MUTEX(pcp_batch_high_lock);
 #define MIN_PERCPU_PAGELIST_FRACTION	(8)
@@ -2068,17 +2071,51 @@ void free_hot_cold_page(struct page *page, bool cold)
 	local_irq_restore(flags);
 }
 
+void update(unsigned long sum, unsigned long count)
+{
+	unsigned long avg;
+
+	if (sum == 0 || count == 0) {
+		return;
+	}
+
+	avg = sum / count;
+	st = avg;
+}
+
 /*
  * Free a list of 0-order pages
  */
 void free_hot_cold_page_list(struct list_head *list, bool cold)
 {
 	struct page *page, *next;
+	struct address_space *mapping;
+	struct inode *inode1;
+	struct timespec t1, now;
+	unsigned long sum = 0, count = 0;
 
 	list_for_each_entry_safe(page, next, list, lru) {
+		printk("Freeing pages\n");
+		mapping = page->mapping;
+		if (!mapping) {
+			printk("No mapping\n");
+			goto out;
+		}
+		inode1 = mapping->host;
+		if (!inode1) {
+			printk("No inode associated\n");
+			goto out;
+		}
+		t1 = inode1->i_atime;
+		getnstimeofday(&now);
+		sum += now.tv_sec - t1.tv_sec;
+		count++;
+
+out:
 		trace_mm_page_free_batched(page, cold);
 		free_hot_cold_page(page, cold);
 	}
+	update(sum, count);
 }
 
 /*