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yaml --- r: 320760 b: refs/heads/master c: df858fa h: refs/heads/master v: v3
git-mirror · Aug 1, 2012 · 47ab19f · 47ab19f
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@@ -1,2 +1,2 @@
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-refs/heads/master: 3fb5c298b04eb6e472f8db1f0fb472749d30041c
+refs/heads/master: df858fa8276f85106f2f5c3cd49c1fa524058070
diff --git a/trunk/Documentation/sysctl/vm.txt b/trunk/Documentation/sysctl/vm.txt
@@ -574,16 +574,24 @@ of physical RAM.  See above.
 
 page-cluster
 
-page-cluster controls the number of pages which are written to swap in
-a single attempt.  The swap I/O size.
+page-cluster controls the number of pages up to which consecutive pages
+are read in from swap in a single attempt. This is the swap counterpart
+to page cache readahead.
+The mentioned consecutivity is not in terms of virtual/physical addresses,
+but consecutive on swap space - that means they were swapped out together.
 
 It is a logarithmic value - setting it to zero means "1 page", setting
 it to 1 means "2 pages", setting it to 2 means "4 pages", etc.
+Zero disables swap readahead completely.
 
 The default value is three (eight pages at a time).  There may be some
 small benefits in tuning this to a different value if your workload is
 swap-intensive.
 
+Lower values mean lower latencies for initial faults, but at the same time
+extra faults and I/O delays for following faults if they would have been part of
+that consecutive pages readahead would have brought in.
+
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 panic_on_oom