The patch titled
readahead: kconfig option READAHEAD_HIT_FEEDBACK
has been added to the -mm tree. Its filename is
readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback.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: kconfig option READAHEAD_HIT_FEEDBACK
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Introduce a kconfig option READAHEAD_HIT_FEEDBACK to enable users to disable
the readahead hit feedback feature.
The readahead hit accounting brings per-page overheads. However it is
necessary for the onseek method, and possible strides method in future.
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
include/linux/fs.h | 14 ++++++++------
include/linux/mm.h | 9 +++++++++
mm/Kconfig | 10 ++++++++++
mm/readahead.c | 27 ++++++++++++++++++++++-----
4 files changed, 49 insertions(+), 11 deletions(-)
diff -puN include/linux/fs.h~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback include/linux/fs.h
--- a/include/linux/fs.h~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback
+++ a/include/linux/fs.h
@@ -647,6 +647,13 @@ struct file_ra_state {
pgoff_t readahead_index;
/*
+ * Snapshot of the (node's) read-ahead aging value
+ * on time of I/O submission.
+ */
+ unsigned long age;
+
+#ifdef CONFIG_READAHEAD_HIT_FEEDBACK
+ /*
* Read-ahead hits.
* i.e. # of distinct read-ahead pages accessed.
*
@@ -659,12 +666,7 @@ struct file_ra_state {
u16 hit1; /* for the current sequence */
u16 hit2; /* for the previous sequence */
u16 hit3; /* for the prev-prev sequence */
-
- /*
- * Snapshot of the (node's) read-ahead aging value
- * on time of I/O submission.
- */
- unsigned long age;
+#endif
};
#endif
};
diff -puN include/linux/mm.h~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback include/linux/mm.h
--- a/include/linux/mm.h~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback
+++ a/include/linux/mm.h
@@ -997,7 +997,16 @@ page_cache_readahead_adaptive(struct add
struct file_ra_state *ra, struct file *filp,
struct page *prev_page, struct page *page,
pgoff_t first_index, pgoff_t index, pgoff_t last_index);
+
+#if defined(CONFIG_READAHEAD_HIT_FEEDBACK) || defined(CONFIG_DEBUG_READAHEAD)
void readahead_cache_hit(struct file_ra_state *ra, struct page *page);
+#else
+static inline void readahead_cache_hit(struct file_ra_state *ra,
+ struct page *page)
+{
+}
+#endif
+
#ifdef CONFIG_ADAPTIVE_READAHEAD
extern int readahead_ratio;
diff -puN mm/Kconfig~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback mm/Kconfig
--- a/mm/Kconfig~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback
+++ a/mm/Kconfig
@@ -215,6 +215,16 @@ config DEBUG_READAHEAD
Say N for production servers.
+config READAHEAD_HIT_FEEDBACK
+ bool "Readahead hit feedback"
+ default y
+ depends on READAHEAD_ALLOW_OVERHEADS
+ help
+ Enable readahead hit feedback.
+
+ It is not needed in normal cases, except for detecting the
+ seek-and-read pattern.
+
config READAHEAD_SMOOTH_AGING
bool "Fine grained readahead aging"
default n
diff -puN mm/readahead.c~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback mm/readahead.c
--- a/mm/readahead.c~readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback
+++ a/mm/readahead.c
@@ -881,8 +881,12 @@ static unsigned long ra_invoke_interval(
*/
static int ra_cache_hit_ok(struct file_ra_state *ra)
{
+#ifdef CONFIG_READAHEAD_HIT_FEEDBACK
return ra->hit0 * readahead_hit_rate >=
(ra->lookahead_index - ra->la_index);
+#else
+ return 1;
+#endif
}
/*
@@ -916,6 +920,7 @@ static void ra_set_class(struct file_ra_
ra->flags = flags | old_ra_class | ra_class;
+#ifdef CONFIG_READAHEAD_HIT_FEEDBACK
/*
* Add request-hit up to sequence-hit and reset the former.
*/
@@ -932,6 +937,7 @@ static void ra_set_class(struct file_ra_
ra->hit2 = ra->hit1;
ra->hit1 = 0;
}
+#endif
}
/*
@@ -1600,6 +1606,7 @@ static int
try_readahead_on_seek(struct file_ra_state *ra, pgoff_t index,
unsigned long ra_size, unsigned long ra_max)
{
+#ifdef CONFIG_READAHEAD_HIT_FEEDBACK
unsigned long hit0 = ra->hit0;
unsigned long hit1 = ra->hit1 + hit0;
unsigned long hit2 = ra->hit2;
@@ -1628,6 +1635,9 @@ try_readahead_on_seek(struct file_ra_sta
ra_set_size(ra, ra_size, 0);
return 1;
+#else
+ return 0;
+#endif
}
/*
@@ -1655,7 +1665,7 @@ thrashing_recovery_readahead(struct addr
ra_size = ra->ra_index - index;
else {
/* After thrashing, we know the exact thrashing-threshold. */
- ra_size = ra->hit0;
+ ra_size = index - ra->ra_index;
update_ra_thrash_bytes(mapping->backing_dev_info, ra_size);
/* And we'd better be a bit conservative. */
@@ -1819,6 +1829,7 @@ readit:
return size;
}
+#if defined(CONFIG_READAHEAD_HIT_FEEDBACK) || defined(CONFIG_DEBUG_READAHEAD)
/**
* readahead_cache_hit - adaptive read-ahead feedback function
* @ra: file_ra_state which holds the readahead state
@@ -1838,13 +1849,16 @@ void readahead_cache_hit(struct file_ra_
if (!ra_has_index(ra, page->index))
return;
+#ifdef CONFIG_READAHEAD_HIT_FEEDBACK
ra->hit0++;
+#endif
if (page->index >= ra->ra_index)
ra_account(ra, RA_EVENT_READAHEAD_HIT, 1);
else
ra_account(ra, RA_EVENT_READAHEAD_HIT, -1);
}
+#endif
/*
* When closing a normal readonly file,
@@ -1860,7 +1874,6 @@ void readahead_close(struct file *file)
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;
@@ -1870,7 +1883,12 @@ void readahead_close(struct file *file)
if (pgcached > bdi->ra_pages0) /* excessive reads */
return;
- pgaccess = max(pgrahit, 1 + pos / PAGE_CACHE_SIZE);
+ pgaccess = 1 + pos / PAGE_CACHE_SIZE;
+#ifdef CONFIG_READAHEAD_HIT_FEEDBACK
+ if (pgaccess < file->f_ra.hit0)
+ pgaccess = file->f_ra.hit0;
+#endif
+
if (pgaccess >= pgcached) {
if (bdi->ra_expect_bytes < bdi->ra_pages0 * PAGE_CACHE_SIZE)
bdi->ra_expect_bytes += pgcached * PAGE_CACHE_SIZE / 8;
@@ -1891,12 +1909,11 @@ void readahead_close(struct file *file)
debug_inc(initial_ra_miss);
dprintk("initial_ra_miss on file %s "
- "size %lluK cached %luK hit %luK "
+ "size %lluK cached %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);
}
_
Patches currently in -mm which might be from wfg@xxxxxxxxxxxxxxxx are
origin.patch
readahead-kconfig-options.patch
readahead-kconfig-option-readahead_allow_overheads.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-sysctl-parameters-fix.patch
readahead-min-max-sizes.patch
readahead-state-based-method-aging-accounting.patch
readahead-state-based-method-routines.patch
readahead-state-based-method-routines-no-ra_flag_eof-on-single-page-file.patch
readahead-state-based-method.patch
readahead-state-based-method-readahead-state-based-method-stand-alone-size-limit-code.patch
readahead-state-based-method-aging-accounting-readahead-kconfig-option-readahead_smooth_aging.patch
readahead-context-based-method.patch
readahead-context-based-method-apply-stream_shift-size-limits-to-contexta-method.patch
readahead-context-based-method-fix-remain-counting.patch
readahead-context-based-method-slow-start.patch
readahead-initial-method-guiding-sizes.patch
readahead-initial-method-guiding-sizes-aggressive-initial-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-backward-prefetching-method-add-use-case-comment.patch
readahead-seeking-reads-method.patch
readahead-thrashing-recovery-method.patch
readahead-call-scheme.patch
readahead-call-scheme-fix-fastcall.patch
readahead-call-scheme-no-fastcall-for-readahead_cache_hit.patch
readahead-call-scheme-no-fastcall-for-readahead_cache_hit-kconfig-option-readahead_hit_feedback.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
readahead-remove-size-limit-on-read_ahead_kb.patch
readahead-backward-prefetching-method-fix.patch
readahead-remove-the-size-limit-of-max_sectors_kb-on-read_ahead_kb.patch
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