The patch titled
readahead: context based method - slow start
has been added to the -mm tree. Its filename is
readahead-context-based-method-slow-start.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: context based method - slow start
From: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
The context method will lead to noticable overhead(readahead miss) on very
sparse random reads.
Having the readahead window to start slowly makes it much better. But
still startup quick if the user prefers sparse readahead.
Benchmarks of reading randomly 100,000 pages on a 1000,000 pages _sparse_
file:
ARA before patch ARA STOCK
================ ================ ================
real 2.779s 2.782s 2.552s 2.606s 2.477s 2.521s
user 1.120s 1.184s 1.133s 1.155s 1.097s 1.159s
sys 1.248s 1.208s 1.093s 1.086s 1.079s 1.064s
Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
mm/readahead.c | 6 ++++++
1 file changed, 6 insertions(+)
diff -puN mm/readahead.c~readahead-context-based-method-slow-start mm/readahead.c
--- a/mm/readahead.c~readahead-context-based-method-slow-start
+++ a/mm/readahead.c
@@ -1439,6 +1439,12 @@ try_context_based_readahead(struct addre
return -1;
} else if (prev_page || probe_page(mapping, index - 1)) {
ra_index = index;
+ /*
+ * Slow start of readahead window.
+ * It helps avoid most readahead miss on sparse random reads.
+ */
+ if (readahead_hit_rate == 1)
+ ra_min = 1;
} else if (readahead_hit_rate > 1) {
ra_index = find_segtail_backward(mapping, index,
readahead_hit_rate + ra_min);
_
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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