Subject: + mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages.patch added to -mm tree
To: raghavendra.kt@xxxxxxxxxxxxxxxxxx,fengguang.wu@xxxxxxxxx,jack@xxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Thu, 06 Feb 2014 14:53:17 -0800
The patch titled
Subject: mm/readahead.c: fix readahead fail for no local memory and limit readahead pages
has been added to the -mm tree. Its filename is
mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages.patch
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From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Subject: mm/readahead.c: fix readahead fail for no local memory and limit readahead pages
max_sane_readahead() returns zero on the cpu having no local memory node.
Fix that by returning a sanitized number of pages viz., minimum of
(requested pages, 4k)
Result:
fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB testfile
32GB* 4G RAM numa machine ( 12 iterations) yielded
Kernel Avg Stddev
base 7.2963 1.10 %
patched 7.2972 1.18 %
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff -puN mm/readahead.c~mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages mm/readahead.c
--- a/mm/readahead.c~mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages
+++ a/mm/readahead.c
@@ -233,14 +233,32 @@ int force_page_cache_readahead(struct ad
return 0;
}
+#define MAX_REMOTE_READAHEAD 4096UL
/*
* Given a desired number of PAGE_CACHE_SIZE readahead pages, return a
* sensible upper limit.
*/
unsigned long max_sane_readahead(unsigned long nr)
{
- return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE_FILE)
- + node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2);
+ unsigned long local_free_page;
+ int nid;
+
+ nid = numa_node_id();
+ if (node_present_pages(nid)) {
+ /*
+ * We sanitize readahead size depending on free memory in
+ * the local node.
+ */
+ local_free_page = node_page_state(nid, NR_INACTIVE_FILE)
+ + node_page_state(nid, NR_FREE_PAGES);
+ return min(nr, local_free_page / 2);
+ }
+ /*
+ * Readahead onto remote memory is better than no readahead when local
+ * numa node does not have memory. We limit the readahead to 4k
+ * pages though to avoid trashing page cache.
+ */
+ return min(nr, MAX_REMOTE_READAHEAD);
}
/*
_
Patches currently in -mm which might be from raghavendra.kt@xxxxxxxxxxxxxxxxxx are
mm-readaheadc-fix-readahead-fail-for-no-local-memory-and-limit-readahead-pages.patch
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