From: Ben Gras <ben@minix3.org>
Date: Wed, 6 Feb 2008 15:05:57 +0000 (+0000)
Subject: Optimization in searching for new zones to allocate contributed
X-Git-Tag: v3.1.4~300
X-Git-Url: http://zhaoyanbai.com/repos/%22http:/www.isc.org/icons/doxygen.png?a=commitdiff_plain;h=2876d5c4bab705a198d1bb08123b6d513cc27714;p=minix.git

Optimization in searching for new zones to allocate contributed
by Jens de Smit.
---

diff --git a/servers/mfs/inode.c b/servers/mfs/inode.c
index 1601bf2f2..690c83f2a 100644
--- a/servers/mfs/inode.c
+++ b/servers/mfs/inode.c
@@ -14,6 +14,9 @@
  *   old_icopy:	   copy to/from in-core inode struct and disk inode (V1.x)
  *   new_icopy:	   copy to/from in-core inode struct and disk inode (V2.x)
  *   dup_inode:	   indicate that someone else is using an inode table entry
+ *
+ * Updates:
+ * 2007-06-01:	jfdsmit@gmail.com added i_zsearch initialization
  */
 
 #include "fs.h"
@@ -204,6 +207,7 @@ int numb;			/* inode number (ANSI: may not be unshort) */
   rip->i_count = 1;
   if (dev != NO_DEV) rw_inode(rip, READING);	/* get inode from disk */
   rip->i_update = 0;		/* all the times are initially up-to-date */
+  rip->i_zsearch = NO_ZONE;	/* no zones searched for yet */
   if ((rip->i_mode & I_TYPE) == I_NAMED_PIPE)
 	rip->i_pipe = I_PIPE;
   else
diff --git a/servers/mfs/inode.h b/servers/mfs/inode.h
index 10e78271a..4fb80fc6d 100644
--- a/servers/mfs/inode.h
+++ b/servers/mfs/inode.h
@@ -6,6 +6,9 @@
  * disk; the second part holds fields not present on the disk.
  * The disk inode part is also declared in "type.h" as 'd1_inode' for V1
  * file systems and 'd2_inode' for V2 file systems.
+ *
+ * Updates:
+ * 2007-01-06: jfdsmit@gmail.com added i_zsearch
  */
 
 #include "queue.h"
@@ -30,6 +33,7 @@ EXTERN struct inode {
   struct super_block *i_sp;	/* pointer to super block for inode's device */
   char i_dirt;			/* CLEAN or DIRTY */
   char i_pipe;			/* set to I_PIPE if pipe */
+  bit_t i_zsearch;		/* where to start search for new zones */
   
   char i_mountpoint;		/* true if mounted on */
 
diff --git a/servers/mfs/write.c b/servers/mfs/write.c
index c51cb0c79..638dc2c9c 100644
--- a/servers/mfs/write.c
+++ b/servers/mfs/write.c
@@ -6,6 +6,9 @@
  *   do_write:     call read_write to perform the WRITE system call
  *   clear_zone:   erase a zone in the middle of a file
  *   new_block:    acquire a new block
+ *
+ * Updates:
+ * 2007-06-01:	jfdsmit@gmail.com added i_zsearch optimalization
  */
 
 #include "fs.h"
@@ -287,18 +290,20 @@ off_t position;			/* file pointer */
 
   /* Is another block available in the current zone? */
   if ( (b = read_map(rip, position)) == NO_BLOCK) {
-	/* Choose first zone if possible. */
-	/* Lose if the file is nonempty but the first zone number is NO_ZONE
-	 * corresponding to a zone full of zeros.  It would be better to
-	 * search near the last real zone.
-	 */
-	if (rip->i_zone[0] == NO_ZONE) {
-		sp = rip->i_sp;
-		z = sp->s_firstdatazone;
+	if (rip->i_zsearch == NO_ZONE) {
+		/* First search for this file. Start looking from
+		 * the file's first data zone to prevent fragmentation
+		 */
+		 if ( (z = rip->i_zone[0]) == NO_ZONE) {
+		 	/* no first zone for file either */
+			z = rip->i_sp->s_firstdatazone; /* let alloc_zone decide */
+		}
 	} else {
-		z = rip->i_zone[0];	/* hunt near first zone */
+		/* searched before, start from last find */
+		z = rip->i_zsearch;
 	}
 	if ( (z = alloc_zone(rip->i_dev, z)) == NO_ZONE) return(NIL_BUF);
+	rip->i_zsearch = z;	/* store for next lookup */
 	if ( (r = write_map(rip, position, z, 0)) != OK) {
 		free_zone(rip->i_dev, z);
 		err_code = r;