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Date: Mon, 12 Jun 2006 16:48:55 -0700 (PDT)
From: Christoph Lameter <clameter@sgi.com>
To: Con Kolivas <kernel@kolivas.org>
cc: linux-kernel@vger.kernel.org, akpm@osdl.org,
       Hugh Dickins <hugh@veritas.com>, Marcelo Tosatti <marcelo@kvack.org>,
       Nick Piggin <nickpiggin@yahoo.com.au>, linux-mm@kvack.org,
       Andi Kleen <ak@suse.de>, Dave Chinner <dgc@sgi.com>
Subject: Re: [PATCH 19/21] swap_prefetch: Conversion of nr_unstable to ZVC
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On Tue, 13 Jun 2006, Con Kolivas wrote:

> Nack. You're changing some other code unintentionally.

Is this okay?

Subject: swap_prefetch: conversion of nr_unstable to per zone counter
From: Christoph Lameter <clameter@sgi.com>

The determination of the vm state is now not that expensive
anymore after we remove the use of the page state.
Remove the logic to avoid the expensive checks.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>

Index: linux-2.6.17-rc6-cl/mm/swap_prefetch.c
===================================================================
--- linux-2.6.17-rc6-cl.orig/mm/swap_prefetch.c	2006-06-12 13:37:47.283159568 -0700
+++ linux-2.6.17-rc6-cl/mm/swap_prefetch.c	2006-06-12 16:46:48.504626417 -0700
@@ -357,7 +357,6 @@ static int prefetch_suitable(void)
 	 */
 	for_each_node_mask(node, sp_stat.prefetch_nodes) {
 		struct node_stats *ns = &sp_stat.node[node];
-		struct page_state ps;
 
 		/*
 		 * We check to see that pages are not being allocated
@@ -375,11 +374,6 @@ static int prefetch_suitable(void)
 		} else
 			ns->last_free = ns->current_free;
 
-		if (!test_pagestate)
-			continue;
-
-		get_page_state_node(&ps, node);
-
 		/* We shouldn't prefetch when we are doing writeback */
 		if (node_page_state(node, NR_WRITEBACK)) {
 			node_clear(node, sp_stat.prefetch_nodes);
@@ -394,7 +388,8 @@ static int prefetch_suitable(void)
 			node_page_state(node, NR_ANON) +
 			node_page_state(node, NR_SLAB) +
 			node_page_state(node, NR_DIRTY) +
-			ps.nr_unstable + total_swapcache_pages;
+			node_page_state(node, NR_UNSTABLE) +
+			total_swapcache_pages;
 		if (limit > ns->prefetch_watermark) {
 			node_clear(node, sp_stat.prefetch_nodes);
 			continue;