lkml.org 
[lkml]   [2006]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH 14/33] readahead: state based method - data structure
Extend struct file_ra_state to support the adaptive read-ahead logic.

Signed-off-by: Wu Fengguang <wfg@mail.ustc.edu.cn>
---
include/linux/fs.h | 57 +++++++++++++++++++++++++++++++++++++++++++----------
1 files changed, 47 insertions(+), 10 deletions(-)
--- linux-2.6.17-rc4-mm3.orig/include/linux/fs.h
+++ linux-2.6.17-rc4-mm3/include/linux/fs.h
@@ -613,21 +613,58 @@ struct fown_struct {

/*
* Track a single file's readahead state
+ *
+ * Diagram for the adaptive readahead logic:
+ *
+ * |--------- old chunk ------->|-------------- new chunk -------------->|
+ * +----------------------------+----------------------------------------+
+ * | # | # |
+ * +----------------------------+----------------------------------------+
+ * ^ ^ ^ ^
+ * file_ra_state.la_index .ra_index .lookahead_index .readahead_index
+ *
+ * Deduced sizes:
+ * |----------- readahead size ------------>|
+ * +----------------------------+----------------------------------------+
+ * | # | # |
+ * +----------------------------+----------------------------------------+
+ * |------- invoke interval ------>|-- lookahead size -->|
*/
struct file_ra_state {
- unsigned long start; /* Current window */
- unsigned long size;
- unsigned long flags; /* ra flags RA_FLAG_xxx*/
- unsigned long cache_hit; /* cache hit count*/
- unsigned long prev_page; /* Cache last read() position */
- unsigned long ahead_start; /* Ahead window */
- unsigned long ahead_size;
- unsigned long ra_pages; /* Maximum readahead window */
- unsigned long mmap_hit; /* Cache hit stat for mmap accesses */
- unsigned long mmap_miss; /* Cache miss stat for mmap accesses */
+ union {
+ struct { /* conventional read-ahead */
+ unsigned long start; /* Current window */
+ unsigned long size;
+ unsigned long ahead_start; /* Ahead window */
+ unsigned long ahead_size;
+ unsigned long cache_hit; /* cache hit count */
+ };
+#ifdef CONFIG_ADAPTIVE_READAHEAD
+ struct { /* adaptive read-ahead */
+ pgoff_t la_index;
+ pgoff_t ra_index;
+ pgoff_t lookahead_index;
+ pgoff_t readahead_index;
+ unsigned long age;
+ uint64_t cache_hits;
+ };
+#endif
+ };
+
+ /* mmap read-around */
+ unsigned long mmap_hit; /* Cache hit stat for mmap accesses */
+ unsigned long mmap_miss; /* Cache miss stat for mmap accesses */
+
+ /* common ones */
+ unsigned long flags; /* ra flags RA_FLAG_xxx*/
+ unsigned long prev_page; /* Cache last read() position */
+ unsigned long ra_pages; /* Maximum readahead window */
};
#define RA_FLAG_MISS 0x01 /* a cache miss occured against this file */
#define RA_FLAG_INCACHE 0x02 /* file is already in cache */
+#define RA_FLAG_MMAP (1UL<<31) /* mmaped page access */
+#define RA_FLAG_NO_LOOKAHEAD (1UL<<30) /* disable look-ahead */
+#define RA_FLAG_EOF (1UL<<29) /* readahead hits EOF */

struct file {
/*
--
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-05-24 13:31    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site