The patch titled
readahead: state based method: prevent tiny size
has been added to the -mm tree. Its filename is
readahead-state-based-method-prevent-tiny-size.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: readahead: state based method: prevent tiny size
From: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
- cancel look-ahead if readahead size is small compared to the look-ahead size,
to avoid too small I/O size, and not to add more memory/io pressure on the
possibly loaded system.
- prevent issuing tiny readahead size, by applying a minimal limit
Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/readahead.c | 21 ++++++++++++++++-----
1 files changed, 16 insertions(+), 5 deletions(-)
diff -puN mm/readahead.c~readahead-state-based-method-prevent-tiny-size mm/readahead.c
--- a/mm/readahead.c~readahead-state-based-method-prevent-tiny-size
+++ a/mm/readahead.c
@@ -928,17 +928,21 @@ static int adjust_rala(unsigned long ra_
unsigned long *ra_size, unsigned long *la_size)
{
/*
- * Substract the old look-ahead to get real safe size for the next
- * read-ahead request.
+ * Cancel asynchrous read-ahead,
+ * if there is a major upsurge of load, or fall of this stream's speed.
*/
- if (*ra_size > *la_size)
- *ra_size -= *la_size;
- else {
+ if (*ra_size <= *la_size * 2) {
ra_account(NULL, RA_EVENT_READAHEAD_SHRINK, *ra_size);
return 0;
}
/*
+ * Substract the old look-ahead to get real safe size for the next
+ * read-ahead request.
+ */
+ *ra_size -= *la_size;
+
+ /*
* Set new la_size according to the (still large) ra_size.
*/
*la_size = *ra_size / LOOKAHEAD_RATIO;
@@ -952,6 +956,13 @@ static void limit_rala(unsigned long ra_
unsigned long stream_shift;
/*
+ * Protect against too small I/O sizes,
+ * by mapping [0, 4*min] to [min, 4*min].
+ */
+ if (*ra_size < 4 * MIN_RA_PAGES)
+ *ra_size = MIN_RA_PAGES + *ra_size * 3 / 4;
+
+ /*
* Apply basic upper limits.
*/
if (*ra_size > ra_max)
_
Patches currently in -mm which might be from wfg@xxxxxxxxxxxxxxxx are
readahead-kconfig-options.patch
readahead-kconfig-options-fix.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-events-accounting-make-readahead_debug_level-static.patch
readahead-rescue_pages.patch
readahead-sysctl-parameters.patch
readahead-sysctl-parameters-use-ctl_unnumbered.patch
readahead-sysctl-parameters-fix.patch
readahead-sysctl-parameters-set-readahead_hit_rate=1.patch
readahead-min-max-sizes.patch
readahead-min-max-sizes-remove-get_readahead_bounds.patch
readahead-min-max-sizes-increase-vm_min_readahead-to-32kb.patch
readahead-state-based-method-aging-accounting.patch
readahead-state-based-method-routines.patch
readahead-state-based-method-routines-explicitly-embed-class_new-class_old-inside-flags.patch
readahead-state-based-method.patch
readahead-state-based-method-prevent-tiny-size.patch
readahead-state-based-method-move-readahead_ratio-out-of-compute_thrashing_threshold.patch
readahead-context-based-method.patch
readahead-context-based-method-locking-fix.patch
readahead-context-based-method-locking-fix-2.patch
readahead-context-based-method-update-ra_min.patch
readahead-context-based-method-remove-readahead_ratio.patch
readahead-initial-method-guiding-sizes.patch
readahead-initial-method-thrashing-guard-size.patch
readahead-initial-method-user-recommended-size.patch
readahead-initial-method-user-recommended-size-rename-to-read_ahead_initial_kb.patch
readahead-initial-method.patch
readahead-backward-prefetching-method.patch
readahead-thrashing-recovery-method.patch
readahead-thrashing-recovery-method-fix.patch
readahead-call-scheme.patch
readahead-call-scheme-ifdef-fix.patch
readahead-call-scheme-build-fix.patch
readahead-call-scheme-remove-get_readahead_bounds.patch
readahead-call-scheme-fix-thrashed-unaligned-read.patch
readahead-laptop-mode.patch
readahead-laptop-mode-fix.patch
readahead-loop-case.patch
readahead-nfsd-case.patch
readahead-nfsd-case-fix.patch
readahead-nfsd-case-fix-uninitialized-ra_min-ra_max.patch
readahead-nfsd-case-remove-ra_min.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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