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 1601bf2f2e59bee7f237f34e6d1992431c3d4d9b..690c83f2abcba3d8fa5ce35be36881b74843f613 100644 (file)
--- 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 10e78271a748af66aa46f3d8a27103b190091e8d..4fb80fc6db058eabc9daad6799aefad9906f0155 100644 (file)
--- 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 c51cb0c79c0cdc19e8fd591512539fc7b06adca9..638dc2c9c5bb3f199b724b409e409701dc2dd143 100644 (file)
--- 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;