The patch titled
readahead: initial method - expected read size
has been added to the -mm tree. Its filename is
readahead-initial-method-expected-read-size.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: readahead: initial method - expected read size
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
backing_dev_info.ra_expect_bytes is dynamicly updated to be the expected
read pages on start-of-file. It allows the initial readahead to be more
aggressive and hence efficient.
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/file_table.c | 7 +++++
include/linux/mm.h | 1
mm/readahead.c | 56 +++++++++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+)
diff -puN fs/file_table.c~readahead-initial-method-expected-read-size fs/file_table.c
--- devel/fs/file_table.c~readahead-initial-method-expected-read-size 2006-05-27 23:06:34.000000000 -0700
+++ devel-akpm/fs/file_table.c 2006-05-27 23:06:34.000000000 -0700
@@ -12,6 +12,7 @@
#include <linux/init.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
+#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/security.h>
#include <linux/eventpoll.h>
@@ -160,6 +161,12 @@ void fastcall __fput(struct file *file)
might_sleep();
fsnotify_close(file);
+
+#ifdef CONFIG_ADAPTIVE_READAHEAD
+ if (file->f_ra.flags & RA_FLAG_EOF)
+ readahead_close(file);
+#endif
+
/*
* The function eventpoll_release() should be the first called
* in the file cleanup chain.
diff -puN include/linux/mm.h~readahead-initial-method-expected-read-size include/linux/mm.h
--- devel/include/linux/mm.h~readahead-initial-method-expected-read-size 2006-05-27 23:06:34.000000000 -0700
+++ devel-akpm/include/linux/mm.h 2006-05-27 23:06:34.000000000 -0700
@@ -991,6 +991,7 @@ unsigned long page_cache_readahead(struc
void handle_ra_miss(struct address_space *mapping,
struct file_ra_state *ra, pgoff_t offset);
unsigned long max_sane_readahead(unsigned long nr);
+void fastcall readahead_close(struct file *file);
#ifdef CONFIG_ADAPTIVE_READAHEAD
extern int readahead_ratio;
diff -puN mm/readahead.c~readahead-initial-method-expected-read-size mm/readahead.c
--- devel/mm/readahead.c~readahead-initial-method-expected-read-size 2006-05-27 23:06:34.000000000 -0700
+++ devel-akpm/mm/readahead.c 2006-05-27 23:06:34.000000000 -0700
@@ -1516,6 +1516,62 @@ static inline void get_readahead_bounds(
(128*1024) / PAGE_CACHE_SIZE), *ra_max / 2);
}
+/*
+ * When closing a normal readonly file,
+ * - on cache hit: increase `backing_dev_info.ra_expect_bytes' slowly;
+ * - on cache miss: decrease it rapidly.
+ *
+ * The resulted `ra_expect_bytes' answers the question of:
+ * How many pages are expected to be read on start-of-file?
+ */
+void fastcall readahead_close(struct file *file)
+{
+ struct inode *inode = file->f_dentry->d_inode;
+ struct address_space *mapping = inode->i_mapping;
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
+ unsigned long pos = file->f_pos; /* supposed to be small */
+ unsigned long pgrahit = file->f_ra.hit0;
+ unsigned long pgcached = mapping->nrpages;
+ unsigned long pgaccess;
+
+ if (!pos) /* pread */
+ return;
+
+ if (pgcached > bdi->ra_pages0) /* excessive reads */
+ return;
+
+ pgaccess = max(pgrahit, 1 + pos / PAGE_CACHE_SIZE);
+ if (pgaccess >= pgcached) {
+ if (bdi->ra_expect_bytes < bdi->ra_pages0 * PAGE_CACHE_SIZE)
+ bdi->ra_expect_bytes += pgcached * PAGE_CACHE_SIZE / 8;
+
+ debug_inc(initial_ra_hit);
+ dprintk("initial_ra_hit on file %s size %lluK "
+ "pos %lu by %s(%d)\n",
+ file->f_dentry->d_name.name,
+ i_size_read(inode) / 1024,
+ pos,
+ current->comm, current->pid);
+ } else {
+ unsigned long missed;
+
+ missed = (pgcached - pgaccess) * PAGE_CACHE_SIZE;
+ if (bdi->ra_expect_bytes >= missed / 2)
+ bdi->ra_expect_bytes -= missed / 2;
+
+ debug_inc(initial_ra_miss);
+ dprintk("initial_ra_miss on file %s "
+ "size %lluK cached %luK hit %luK "
+ "pos %lu by %s(%d)\n",
+ file->f_dentry->d_name.name,
+ i_size_read(inode) / 1024,
+ pgcached << (PAGE_CACHE_SHIFT - 10),
+ pgrahit << (PAGE_CACHE_SHIFT - 10),
+ pos,
+ current->comm, current->pid);
+ }
+}
+
#endif /* CONFIG_ADAPTIVE_READAHEAD */
/*
_
Patches currently in -mm which might be from wfg@xxxxxxxxxxxxxxxx are
readahead-kconfig-options.patch
radixtree-introduce-radix_tree_scan_hole.patch
mm-introduce-probe_page.patch
mm-introduce-pg_readahead.patch
readahead-add-look-ahead-support-to-__do_page_cache_readahead.patch
readahead-delay-page-release-in-do_generic_mapping_read.patch
readahead-insert-cond_resched-calls.patch
readahead-minmax_ra_pages.patch
readahead-events-accounting.patch
readahead-rescue_pages.patch
readahead-sysctl-parameters.patch
readahead-min-max-sizes.patch
readahead-state-based-method-aging-accounting.patch
readahead-state-based-method-routines.patch
readahead-state-based-method.patch
readahead-context-based-method.patch
readahead-initial-method-guiding-sizes.patch
readahead-initial-method-thrashing-guard-size.patch
readahead-initial-method-expected-read-size.patch
readahead-initial-method-user-recommended-size.patch
readahead-initial-method.patch
readahead-backward-prefetching-method.patch
readahead-seeking-reads-method.patch
readahead-thrashing-recovery-method.patch
readahead-call-scheme.patch
readahead-laptop-mode.patch
readahead-loop-case.patch
readahead-nfsd-case.patch
readahead-turn-on-by-default.patch
readahead-debug-radix-tree-new-functions.patch
readahead-debug-traces-showing-accessed-file-names.patch
readahead-debug-traces-showing-read-patterns.patch
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