The patch titled
readahead: initial method - thrashing guard size
has been added to the -mm tree. Its filename is
readahead-initial-method-thrashing-guard-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 - thrashing guard size
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
backing_dev_info.ra_thrash_bytes is dynamicly updated to be a little above
the thrashing safe read-ahead size. It is used in the initial method where
the thrashing threshold for the particular reader is still unknown.
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/readahead.c | 20 ++++++++++++++++++++
1 files changed, 20 insertions(+)
diff -puN mm/readahead.c~readahead-initial-method-thrashing-guard-size mm/readahead.c
--- a/mm/readahead.c~readahead-initial-method-thrashing-guard-size
+++ a/mm/readahead.c
@@ -787,6 +787,22 @@ out:
}
/*
+ * Update `backing_dev_info.ra_thrash_bytes' to be a _biased_ average of
+ * read-ahead sizes. Which makes it an a-bit-risky(*) estimation of the
+ * _minimal_ read-ahead thrashing threshold on the device.
+ *
+ * (*) Note that being a bit risky can _help_ overall performance.
+ */
+static void update_ra_thrash_bytes(struct backing_dev_info *bdi,
+ unsigned long ra_size)
+{
+ ra_size <<= PAGE_CACHE_SHIFT;
+ bdi->ra_thrash_bytes = (bdi->ra_thrash_bytes < ra_size) ?
+ (ra_size + bdi->ra_thrash_bytes * 127) / 128:
+ (ra_size + bdi->ra_thrash_bytes * 7) / 8;
+}
+
+/*
* Some helpers for querying/building a read-ahead request.
*
* Diagram for some variable names used frequently:
@@ -1083,6 +1099,10 @@ state_based_readahead(struct address_spa
limit_rala(growth_limit, la_old, &ra_size, &la_size);
+ /* ra_size in its _steady_ state reflects thrashing threshold */
+ if (page && ra_old + ra_old / 8 >= ra_size)
+ update_ra_thrash_bytes(mapping->backing_dev_info, ra_size);
+
ra_set_class(ra, RA_CLASS_STATE);
ra_set_index(ra, offset, ra->readahead_index);
ra_set_size(ra, ra_size, la_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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