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Date: Fri, 25 Jan 2013 17:58:11 -0800 (PST)
From: Hugh Dickins <hughd@...gle.com>
To: Andrew Morton <akpm@...ux-foundation.org>
cc: Petr Holasek <pholasek@...hat.com>,
Andrea Arcangeli <aarcange@...hat.com>,
Izik Eidus <izik.eidus@...ellosystems.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: [PATCH 3/11] ksm: trivial tidyups
Add NUMA() and DO_NUMA() macros to minimize blight of #ifdef CONFIG_NUMAs
(but indeed we don't want to expand struct rmap_item by nid when not NUMA).
Add comment, remove "unsigned" from rmap_item->nid, as "int nid" elsewhere.
Define ksm_merge_across_nodes 1U when #ifndef NUMA to help optimizing out.
Use ?: in get_kpfn_nid(). Adjust a few comments noticed in ongoing work.
Leave stable_tree_insert()'s rb_linkage until after the node has been set
up, as unstable_tree_search_insert() does: ksm_thread_mutex and page lock
make either way safe, but we're going to copy and I prefer this precedent.
Signed-off-by: Hugh Dickins <hughd@...gle.com>
---
mm/ksm.c | 48 ++++++++++++++++++++++--------------------------
1 file changed, 22 insertions(+), 26 deletions(-)
--- mmotm.orig/mm/ksm.c 2013-01-25 14:36:38.608205618 -0800
+++ mmotm/mm/ksm.c 2013-01-25 14:36:52.152205940 -0800
@@ -41,6 +41,14 @@
#include <asm/tlbflush.h>
#include "internal.h"
+#ifdef CONFIG_NUMA
+#define NUMA(x) (x)
+#define DO_NUMA(x) (x)
+#else
+#define NUMA(x) (0)
+#define DO_NUMA(x) do { } while (0)
+#endif
+
/*
* A few notes about the KSM scanning process,
* to make it easier to understand the data structures below:
@@ -130,6 +138,7 @@ struct stable_node {
* @mm: the memory structure this rmap_item is pointing into
* @address: the virtual address this rmap_item tracks (+ flags in low bits)
* @oldchecksum: previous checksum of the page at that virtual address
+ * @nid: NUMA node id of unstable tree in which linked (may not match page)
* @node: rb node of this rmap_item in the unstable tree
* @head: pointer to stable_node heading this list in the stable tree
* @hlist: link into hlist of rmap_items hanging off that stable_node
@@ -141,7 +150,7 @@ struct rmap_item {
unsigned long address; /* + low bits used for flags below */
unsigned int oldchecksum; /* when unstable */
#ifdef CONFIG_NUMA
- unsigned int nid;
+ int nid;
#endif
union {
struct rb_node node; /* when node of unstable tree */
@@ -192,8 +201,12 @@ static unsigned int ksm_thread_pages_to_
/* Milliseconds ksmd should sleep between batches */
static unsigned int ksm_thread_sleep_millisecs = 20;
+#ifdef CONFIG_NUMA
/* Zeroed when merging across nodes is not allowed */
static unsigned int ksm_merge_across_nodes = 1;
+#else
+#define ksm_merge_across_nodes 1U
+#endif
#define KSM_RUN_STOP 0
#define KSM_RUN_MERGE 1
@@ -456,10 +469,7 @@ out: page = NULL;
*/
static inline int get_kpfn_nid(unsigned long kpfn)
{
- if (ksm_merge_across_nodes)
- return 0;
- else
- return pfn_to_nid(kpfn);
+ return ksm_merge_across_nodes ? 0 : pfn_to_nid(kpfn);
}
static void remove_node_from_stable_tree(struct stable_node *stable_node)
@@ -479,7 +489,6 @@ static void remove_node_from_stable_tree
}
nid = get_kpfn_nid(stable_node->kpfn);
-
rb_erase(&stable_node->node, &root_stable_tree[nid]);
free_stable_node(stable_node);
}
@@ -578,13 +587,8 @@ static void remove_rmap_item_from_tree(s
age = (unsigned char)(ksm_scan.seqnr - rmap_item->address);
BUG_ON(age > 1);
if (!age)
-#ifdef CONFIG_NUMA
rb_erase(&rmap_item->node,
- &root_unstable_tree[rmap_item->nid]);
-#else
- rb_erase(&rmap_item->node, &root_unstable_tree[0]);
-#endif
-
+ &root_unstable_tree[NUMA(rmap_item->nid)]);
ksm_pages_unshared--;
rmap_item->address &= PAGE_MASK;
}
@@ -604,7 +608,7 @@ static void remove_trailing_rmap_items(s
}
/*
- * Though it's very tempting to unmerge in_stable_tree(rmap_item)s rather
+ * Though it's very tempting to unmerge rmap_items from stable tree rather
* than check every pte of a given vma, the locking doesn't quite work for
* that - an rmap_item is assigned to the stable tree after inserting ksm
* page and upping mmap_sem. Nor does it fit with the way we skip dup'ing
@@ -1058,7 +1062,7 @@ static struct page *stable_tree_search(s
}
/*
- * stable_tree_insert - insert rmap_item pointing to new ksm page
+ * stable_tree_insert - insert stable tree node pointing to new ksm page
* into the stable tree.
*
* This function returns the stable tree node just allocated on success,
@@ -1108,13 +1112,11 @@ static struct stable_node *stable_tree_i
if (!stable_node)
return NULL;
- rb_link_node(&stable_node->node, parent, new);
- rb_insert_color(&stable_node->node, &root_stable_tree[nid]);
-
INIT_HLIST_HEAD(&stable_node->hlist);
-
stable_node->kpfn = kpfn;
set_page_stable_node(kpage, stable_node);
+ rb_link_node(&stable_node->node, parent, new);
+ rb_insert_color(&stable_node->node, &root_stable_tree[nid]);
return stable_node;
}
@@ -1170,8 +1172,6 @@ struct rmap_item *unstable_tree_search_i
* If tree_page has been migrated to another NUMA node, it
* will be flushed out and put into the right unstable tree
* next time: only merge with it if merge_across_nodes.
- * Just notice, we don't have similar problem for PageKsm
- * because their migration is disabled now. (62b61f611e)
*/
if (!ksm_merge_across_nodes && page_to_nid(tree_page) != nid) {
put_page(tree_page);
@@ -1195,9 +1195,7 @@ struct rmap_item *unstable_tree_search_i
rmap_item->address |= UNSTABLE_FLAG;
rmap_item->address |= (ksm_scan.seqnr & SEQNR_MASK);
-#ifdef CONFIG_NUMA
- rmap_item->nid = nid;
-#endif
+ DO_NUMA(rmap_item->nid = nid);
rb_link_node(&rmap_item->node, parent, new);
rb_insert_color(&rmap_item->node, root);
@@ -1213,13 +1211,11 @@ struct rmap_item *unstable_tree_search_i
static void stable_tree_append(struct rmap_item *rmap_item,
struct stable_node *stable_node)
{
-#ifdef CONFIG_NUMA
/*
* Usually rmap_item->nid is already set correctly,
* but it may be wrong after switching merge_across_nodes.
*/
- rmap_item->nid = get_kpfn_nid(stable_node->kpfn);
-#endif
+ DO_NUMA(rmap_item->nid = get_kpfn_nid(stable_node->kpfn));
rmap_item->head = stable_node;
rmap_item->address |= STABLE_FLAG;
hlist_add_head(&rmap_item->hlist, &stable_node->hlist);
--
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