The patch titled
readahead: thrashing recovery method
has been added to the -mm tree. Its filename is
readahead-thrashing-recovery-method.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: thrashing recovery method
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Readahead policy after thrashing.
It tries to recover gracefully from the thrashing.
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/readahead.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 44 insertions(+)
diff -puN mm/readahead.c~readahead-thrashing-recovery-method mm/readahead.c
--- a/mm/readahead.c~readahead-thrashing-recovery-method
+++ a/mm/readahead.c
@@ -1487,6 +1487,50 @@ try_backward_prefetching(struct file_ra_
}
/*
+ * Readahead thrashing recovery.
+ */
+static unsigned long
+thrashing_recovery_readahead(struct address_space *mapping,
+ struct file *filp, struct file_ra_state *ra,
+ pgoff_t offset, unsigned long ra_max)
+{
+ unsigned long ra_size;
+
+#ifdef CONFIG_DEBUG_READAHEAD
+ if (probe_page(mapping, offset - 1))
+ ra_account(ra, RA_EVENT_READAHEAD_MUTILATE,
+ ra->readahead_index - offset);
+ ra_account(ra, RA_EVENT_READAHEAD_THRASHING,
+ ra->readahead_index - offset);
+#endif
+
+ /*
+ * Some thrashing occur in (ra_index, la_index], in which case the
+ * old read-ahead chunk is lost soon after the new one is allocated.
+ * Ensure that we recover all needed pages in the old chunk.
+ */
+ if (offset < ra->ra_index)
+ ra_size = ra->ra_index - offset;
+ else {
+ /* After thrashing, we know the exact thrashing-threshold. */
+ ra_size = offset - ra->ra_index;
+ update_ra_thrash_bytes(mapping->backing_dev_info, ra_size);
+
+ /* And we'd better be a bit conservative. */
+ ra_size = ra_size * 3 / 4;
+ }
+
+ if (ra_size > ra_max)
+ ra_size = ra_max;
+
+ ra_set_class(ra, RA_CLASS_THRASHING);
+ ra_set_index(ra, offset, offset);
+ ra_set_size(ra, ra_size, ra_size / LOOKAHEAD_RATIO);
+
+ return ra_submit(ra, mapping, filp);
+}
+
+/*
* ra_min is mainly determined by the size of cache memory. Reasonable?
*
* Table of concrete numbers for 4KB page size:
_
Patches currently in -mm which might be from wfg@xxxxxxxxxxxxxxxx are
readahead-kconfig-options.patch
radixtree-introduce-scan-hole-data-functions.patch
mm-introduce-probe_page.patch
mm-introduce-pg_readahead.patch
readahead-add-look-ahead-support-to-__do_page_cache_readahead.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-user-recommended-size.patch
readahead-initial-method.patch
readahead-backward-prefetching-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-remove-size-limit-on-read_ahead_kb.patch
readahead-remove-size-limit-of-max_sectors_kb-on-read_ahead_kb.patch
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