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authorRaghavendra K T <raghavendra.kt@linux.vnet.ibm.com>2014-04-03 14:48:23 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-10-09 12:21:28 -0700
commitd4995db1ea96e5f357b92469c9b6c3ecc6bdfbaa (patch)
treec704c4aaa6e8ae74823a81e1972ea7c9e8998e4f /kernel
parent67c58ce60024b9b3d9cf203da994bf265aa7e369 (diff)
mm/readahead.c: fix readahead failure for memoryless NUMA nodes and limit readahead pages
commit 6d2be915e589b58cb11418cbe1f22ff90732b6ac upstream. 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@linux-foundation.org> Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com> Acked-by: Jan Kara <jack@suse.cz> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'kernel')
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