Subject: + mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages.patch added to -mm tree
To: raghavendra.kt@xxxxxxxxxxxxxxxxxx,fengguang.wu@xxxxxxxxx,jack@xxxxxxx,rientjes@xxxxxxxxxx,torvalds@xxxxxxxxxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Tue, 18 Feb 2014 13:17:26 -0800
The patch titled
Subject: mm/readahead.c: fix readahead failure for memoryless NUMA nodes and limit readahead pages
has been added to the -mm tree. Its filename is
mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages.patch
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From: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Subject: mm/readahead.c: fix readahead failure for memoryless NUMA nodes and limit readahead pages
Currently max_sane_readahead() returns zero on the cpu whose NUMA node has
no local memory which leads to readahead failure. Fix this readahead
failure by returning minimum of (requested pages, 512). Users running
applications on a memory-less cpu which needs readahead such as streaming
application see considerable boost in the performance.
Result:
fadvise experiment with FADV_WILLNEED on a PPC machine having memoryless
CPU with 1GB testfile (12 iterations) yielded around 46.66% improvement.
fadvise experiment with FADV_WILLNEED on a x240 machine with 1GB testfile
32GB* 4G RAM numa machine (12 iterations) showed no impact on the normal
NUMA cases w/ patch.
Kernel Avg Stddev
base 7.4975 3.92%
patched 7.4174 3.26%
[Andrew: making return value PAGE_SIZE independent]
Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Acked-by: Jan Kara <jack@xxxxxxx>
Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
Cc: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/readahead.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff -puN mm/readahead.c~mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages mm/readahead.c
--- a/mm/readahead.c~mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages
+++ a/mm/readahead.c
@@ -233,14 +233,14 @@ int force_page_cache_readahead(struct ad
return 0;
}
+#define MAX_READAHEAD ((512*4096)/PAGE_CACHE_SIZE)
/*
* 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);
+ return min(nr, MAX_READAHEAD);
}
/*
_
Patches currently in -mm which might be from raghavendra.kt@xxxxxxxxxxxxxxxxxx are
mm-readaheadc-fix-readahead-failure-for-memoryless-numa-nodes-and-limit-readahead-pages.patch
linux-next.patch
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