Skip to content

Commit

Permalink
ksm: trivial tidyups
Browse files Browse the repository at this point in the history 
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@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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
  • Loading branch information
Hugh Dickins authored and Linus Torvalds committed Feb 24, 2013
1 parent f00dc0e commit e850dcf
Showing 1 changed file with 22 additions and 26 deletions.
48 changes: 22 additions & 26 deletions mm/ksm.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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:
Expand Down Expand Up @@ -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
Expand All @@ -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 */
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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)
Expand All @@ -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);
}
Expand Down Expand Up @@ -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;
}
Expand All @@ -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
Expand Down Expand Up @@ -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,
Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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);
Expand All @@ -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);

Expand All @@ -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);
Expand Down

0 comments on commit e850dcf

Please sign in to comment.