Commit e850dcf5 authored by Hugh Dickins's avatar Hugh Dickins Committed by Linus Torvalds
Browse files

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: default avatarHugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Petr Holasek <pholasek@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Izik Eidus <izik.eidus@ravellosystems.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f00dc0ee

mm/ksm.c

+22 −26
Original line number Diff line number Diff line
@@ -41,6 +41,14 @@ 
#include <asm/tlbflush.h>

#include "internal.h"



#ifdef CONFIG_NUMA

#define NUMA(x)		(x)

#define DO_NUMA(x)	do { (x); } while (0)

#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_scan = 100; 
/* 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(struct stable_node *stable_node) 
	}



	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(struct rmap_item *rmap_item) 
		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(struct mm_slot *mm_slot, 
}



/*

 * 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(struct page *page) 
}



/*

 * 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_insert(struct page *kpage) 
	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_insert(struct rmap_item *rmap_item, 
		 * 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_insert(struct rmap_item *rmap_item, 


	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_insert(struct rmap_item *rmap_item, 
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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