The patch titled
readahead: initial method
has been removed from the -mm tree. Its filename was
readahead-initial-method.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
Subject: readahead: initial method
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Aggressive readahead policy for read on start-of-file.
Instead of selecting a conservative readahead size,
it tries to do large readahead in the first place.
However we have to watch on two cases:
- do not ruin the hit rate for file-head-checkers
- do not lead to thrashing for memory tight systems
In most cases, the threat of file-head-peakers is neglectable. So a simple
user tunable parameter is used. Users can try a larger initial read-ahead
size:
echo 128 > /sys/block/sda/queue/initial_ra_kb
It benefits the many-small-files case:
adaptive readahead: avg 10.3 seconds
====================================
stock readahead: avg 12.3 seconds
=================================
The rxvt-unicode-7.7 being benchmarked is a dir with many .C/.h/.o files.
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)
diff -puN mm/readahead.c~readahead-initial-method mm/readahead.c
--- a/mm/readahead.c~readahead-initial-method
+++ a/mm/readahead.c
@@ -1458,6 +1458,42 @@ has_history_pages:
return 1;
}
+/*
+ * Read-ahead on start of file.
+ *
+ * We want to be as aggressive as possible, _and_
+ * - do not ruin the hit rate for file-head-peekers
+ * - do not lead to thrashing for memory tight systems
+ */
+static unsigned long
+initial_readahead(struct address_space *mapping, struct file *filp,
+ struct file_ra_state *ra, unsigned long req_size)
+{
+ struct backing_dev_info *bdi = mapping->backing_dev_info;
+ unsigned long thrash_pages = bdi->ra_thrash_bytes >> PAGE_CACHE_SHIFT;
+ unsigned long ra_size;
+ unsigned long la_size;
+
+ ra_size = req_size;
+
+ /* user imposed minimal size */
+ if (ra_size < bdi->ra_pages0)
+ ra_size = bdi->ra_pages0;
+
+ /* no read-ahead thrashing */
+ if (ra_size > thrash_pages)
+ ra_size = thrash_pages;
+
+ /* do look-ahead on large(>= 32KB) read-ahead */
+ la_size = ra_size / LOOKAHEAD_RATIO;
+
+ ra_set_class(ra, RA_CLASS_INITIAL);
+ ra_set_index(ra, 0, 0);
+ ra_set_size(ra, ra_size, la_size);
+
+ return ra_submit(ra, mapping, filp);
+}
+
#endif /* CONFIG_ADAPTIVE_READAHEAD */
/*
_
Patches currently in -mm which might be from wfg@xxxxxxxxxxxxxxxx are
origin.patch
readahead-initial-method.patch
readahead-backward-prefetching-method.patch
readahead-thrashing-recovery-method.patch
readahead-thrashing-recovery-method-check-unbalanced-aging.patch
readahead-thrashing-recovery-method-refill-holes.patch
readahead-call-scheme.patch
readahead-call-scheme-cleanup.patch
readahead-call-scheme-catch-thrashing-on-lookahead-time.patch
readahead-call-scheme-doc-fixes-for-readahead.patch
readahead-laptop-mode.patch
readahead-loop-case.patch
readahead-nfsd-case.patch
readahead-remove-parameter-ra_max-from-thrashing_recovery_readahead.patch
readahead-remove-parameter-ra_max-from-adjust_rala.patch
readahead-state-based-method-protect-against-tiny-size.patch
readahead-rename-state_based_readahead-to-clock_based_readahead.patch
readahead-account-i-o-block-times-for-stock-readahead.patch
readahead-rescue_pages-updates.patch
readahead-remove-noaction-shrink-events.patch
readahead-remove-size-limit-on-read_ahead_kb.patch
readahead-remove-size-limit-of-max_sectors_kb-on-read_ahead_kb.patch
readahead-partial-sendfile-fix.patch
readahead-turn-on-by-default.patch
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