[PATCH 4/6] readahead: kconfig option READAHEAD_SMOOTH_AGING

[Wu Fengguang]

Make the kconfig option READAHEAD_SMOOTH_AGING depend on
READAHEAD_ALLOW_OVERHEADS, and turned off by default.

Signed-off-by: Wu Fengguang <wfg@xxxxxxxxxxxxxxxx>
---


--- linux-2.6.17-mm2.orig/mm/Kconfig
+++ linux-2.6.17-mm2/mm/Kconfig
@@ -216,6 +216,14 @@ config DEBUG_READAHEAD
 	  Say N for production servers.
 
 config READAHEAD_SMOOTH_AGING
-	def_bool n if NUMA
-	default y if !NUMA
-	depends on ADAPTIVE_READAHEAD
+	bool "Fine grained readahead aging"
+	default n
+	depends on READAHEAD_ALLOW_OVERHEADS && !NUMA
+	help
+	  Enable fine grained, mooth accounting of readahead aging.
+
+	  It can help servers which meet the following two conditions:
+	  	- have large number of concurrent readers
+		- have the danger of readahead thrashing(i.e. memory tight)
+
+	  This feature is only available on non-NUMA systems.

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