Changeset dba4a23 in mainline

Timestamp:

2010-07-28T15:22:22Z (14 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

4637c72, 9a1d8ab

Parents:

6da81e0

Message:

Speed up sequential I/O by caching the "current" cluster in fat_block_get().
This improves sequentil read of a 5m file (using the cat command) by 45 seconds
(73s → 28s).

Location:

uspace/srv/fs/fat

Files:

• fat.h (modified) (1 diff)
• fat_fat.c (modified) (4 diffs)
• fat_ops.c (modified) (1 diff)

uspace/srv/fs/fat/fat.h

@@ -213 +213 @@
 
         /*
-         * Cache of the node's last cluster to avoid some unnecessary FAT walks.
+         * Cache of the node's last and "current" cluster to avoid some
+         * unnecessary FAT walks.
          */
-        bool                    lastc_cached_valid;
-        fat_cluster_t           lastc_cached_value;
+        /* Node's last cluster in FAT. */
+        bool            lastc_cached_valid;
+        fat_cluster_t   lastc_cached_value;
+        /* Node's "current" cluster, i.e. where the last I/O took place. */
+        bool            currc_cached_valid;
+        aoff64_t        currc_cached_bn;
+        fat_cluster_t   currc_cached_value;
 } fat_node_t;
 

uspace/srv/fs/fat/fat_fat.c

@@ -142 +142 @@
     aoff64_t bn, int flags)
 {
+        fat_cluster_t firstc = nodep->firstc;
+        fat_cluster_t currc;
+        aoff64_t relbn = bn;
+        int rc;
+
         if (!nodep->size)
                 return ELIMIT;
@@ -158 +163 @@
         }
 
+        if (nodep->currc_cached_valid && bn >= nodep->currc_cached_bn) {
+                /*
+                 * We can start with the cluster cached by the previous call to
+                 * fat_block_get().
+                 */
+                firstc = nodep->currc_cached_value;
+                relbn -= (nodep->currc_cached_bn / SPC(bs)) * SPC(bs);
+        }
+
 fall_through:
-        return _fat_block_get(block, bs, nodep->idx->dev_handle, nodep->firstc,
-            NULL, bn, flags);
+        rc = _fat_block_get(block, bs, nodep->idx->dev_handle, firstc,
+            &currc, relbn, flags);
+        if (rc != EOK)
+                return rc;
+        
+        /*
+         * Update the "current" cluster cache.
+         */
+        nodep->currc_cached_valid = true;
+        nodep->currc_cached_bn = bn;
+        nodep->currc_cached_value = currc;
+
+        return rc;
 }
 
@@ -567 +592 @@
         dev_handle_t dev_handle = nodep->idx->dev_handle;
 
+        /*
+         * Invalidate cached cluster numbers.
+         */
         nodep->lastc_cached_valid = false;
+        if (nodep->currc_cached_value != lcl)
+                nodep->currc_cached_valid = false;
+
         if (lcl == FAT_CLST_RES0) {
                 /* The node will have zero size and no clusters allocated. */
@@ -597 +628 @@
         }
 
+        /*
+         * Update and re-enable the last cluster cache.
+         */
         nodep->lastc_cached_valid = true;
         nodep->lastc_cached_value = lcl;

uspace/srv/fs/fat/fat_ops.c

@@ -106 +106 @@
         node->lastc_cached_valid = false;
         node->lastc_cached_value = FAT_CLST_LAST1;
+        node->currc_cached_valid = false;
+        node->currc_cached_bn = 0;
+        node->currc_cached_value = FAT_CLST_LAST1;
 }