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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v5 1/8] mm: Place unscrubbed pages at the end of pagelist
. so that it's easy to find pages that need to be scrubbed (those pages are
now marked with _PGC_need_scrub bit).
We keep track of the first unscrubbed page in a page buddy using first_dirty
field. For now it can have two values, 0 (whole buddy needs scrubbing) or
INVALID_DIRTY_IDX (the buddy does not need to be scrubbed). Subsequent patches
will allow scrubbing to be interrupted, resulting in first_dirty taking any
value.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
Changes in v5:
* Be more careful when returning unused portion of a buddy to the heap in
alloc_heap_pages() and don't set first_dirty if we know that the sub-buddy
is clean
* In reserve_offlined_page(), don't try to find dirty pages in sub-buddies if we
can figure out that there is none.
* Drop unnecessary setting of first_dirty in free_heap_pages()
* Switch to using bitfields in page_info.u.free
I kept node_need_scrub[] as a global array and not a "per-node". I think
splitting
it should be part of making heap_lock a per-node lock, together with increasing
scrub concurrency by having more than one CPU scrub a node.
xen/common/page_alloc.c | 190 +++++++++++++++++++++++++++++++++++++++--------
xen/include/asm-arm/mm.h | 18 ++++-
xen/include/asm-x86/mm.h | 17 ++++-
3 files changed, 190 insertions(+), 35 deletions(-)
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 8bcef6a..570d1f7 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -383,6 +383,8 @@ typedef struct page_list_head
heap_by_zone_and_order_t[NR_ZONES][MAX_ORDER+1];
static heap_by_zone_and_order_t *_heap[MAX_NUMNODES];
#define heap(node, zone, order) ((*_heap[node])[zone][order])
+static unsigned long node_need_scrub[MAX_NUMNODES];
+
static unsigned long *avail[MAX_NUMNODES];
static long total_avail_pages;
@@ -678,6 +680,20 @@ static void check_low_mem_virq(void)
}
}
+/* Pages that need a scrub are added to tail, otherwise to head. */
+static void page_list_add_scrub(struct page_info *pg, unsigned int node,
+ unsigned int zone, unsigned int order,
+ unsigned int first_dirty)
+{
+ PFN_ORDER(pg) = order;
+ pg->u.free.first_dirty = first_dirty;
+
+ if ( first_dirty != INVALID_DIRTY_IDX )
+ page_list_add_tail(pg, &heap(node, zone, order));
+ else
+ page_list_add(pg, &heap(node, zone, order));
+}
+
/* Allocate 2^@order contiguous pages. */
static struct page_info *alloc_heap_pages(
unsigned int zone_lo, unsigned int zone_hi,
@@ -687,7 +703,7 @@ static struct page_info *alloc_heap_pages(
unsigned int i, j, zone = 0, nodemask_retry = 0;
nodeid_t first_node, node = MEMF_get_node(memflags), req_node = node;
unsigned long request = 1UL << order;
- struct page_info *pg;
+ struct page_info *pg, *first_dirty_pg = NULL;
nodemask_t nodemask = (d != NULL ) ? d->node_affinity : node_online_map;
bool_t need_tlbflush = 0;
uint32_t tlbflush_timestamp = 0;
@@ -798,11 +814,26 @@ static struct page_info *alloc_heap_pages(
return NULL;
found:
+
+ if ( pg->u.free.first_dirty != INVALID_DIRTY_IDX )
+ first_dirty_pg = pg + pg->u.free.first_dirty;
+
/* We may have to halve the chunk a number of times. */
while ( j != order )
{
- PFN_ORDER(pg) = --j;
- page_list_add_tail(pg, &heap(node, zone, j));
+ unsigned int first_dirty;
+
+ if ( first_dirty_pg && ((pg + (1 << j)) > first_dirty_pg) )
+ {
+ if ( pg < first_dirty_pg )
+ first_dirty = (first_dirty_pg - pg) / sizeof(*pg);
+ else
+ first_dirty = 0;
+ }
+ else
+ first_dirty = INVALID_DIRTY_IDX;
+
+ page_list_add_scrub(pg, node, zone, --j, first_dirty);
pg += 1 << j;
}
@@ -849,13 +880,22 @@ static int reserve_offlined_page(struct page_info *head)
{
unsigned int node = phys_to_nid(page_to_maddr(head));
int zone = page_to_zone(head), i, head_order = PFN_ORDER(head), count = 0;
- struct page_info *cur_head;
+ struct page_info *cur_head, *first_dirty_pg = NULL;
int cur_order;
ASSERT(spin_is_locked(&heap_lock));
cur_head = head;
+ /*
+ * We may break the buddy so let's mark the head as clean. Then, when
+ * merging chunks back into the heap, we will see whether the chunk has
+ * unscrubbed pages and set its first_dirty properly.
+ */
+ if (head->u.free.first_dirty != INVALID_DIRTY_IDX)
+ first_dirty_pg = head + head->u.free.first_dirty;
+ head->u.free.first_dirty = INVALID_DIRTY_IDX;
+
page_list_del(head, &heap(node, zone, head_order));
while ( cur_head < (head + (1 << head_order)) )
@@ -873,6 +913,8 @@ static int reserve_offlined_page(struct page_info *head)
while ( cur_order < head_order )
{
+ unsigned int first_dirty = INVALID_DIRTY_IDX;
+
next_order = cur_order + 1;
if ( (cur_head + (1 << next_order)) >= (head + ( 1 << head_order))
)
@@ -892,8 +934,25 @@ static int reserve_offlined_page(struct page_info *head)
{
merge:
/* We don't consider merging outside the head_order. */
- page_list_add_tail(cur_head, &heap(node, zone, cur_order));
- PFN_ORDER(cur_head) = cur_order;
+
+ /* See if any of the pages indeed need scrubbing. */
+ if ( first_dirty_pg && (cur_head + (1 << cur_order) >
first_dirty_pg) )
+ {
+ if ( cur_head < first_dirty_pg )
+ i = (first_dirty_pg - cur_head) / sizeof(*cur_head);
+ else
+ i = 0;
+
+ for ( ; i < (1 << cur_order); i++ )
+ if ( test_bit(_PGC_need_scrub,
+ &cur_head[i].count_info) )
+ {
+ first_dirty = i;
+ break;
+ }
+ }
+ page_list_add_scrub(cur_head, node, zone,
+ cur_order, first_dirty);
cur_head += (1 << cur_order);
break;
}
@@ -919,9 +978,53 @@ static int reserve_offlined_page(struct page_info *head)
return count;
}
+static void scrub_free_pages(unsigned int node)
+{
+ struct page_info *pg;
+ unsigned int zone;
+
+ ASSERT(spin_is_locked(&heap_lock));
+
+ if ( !node_need_scrub[node] )
+ return;
+
+ for ( zone = 0; zone < NR_ZONES; zone++ )
+ {
+ unsigned int order = MAX_ORDER;
+
+ do {
+ while ( !page_list_empty(&heap(node, zone, order)) )
+ {
+ unsigned int i;
+
+ /* Unscrubbed pages are always at the end of the list. */
+ pg = page_list_last(&heap(node, zone, order));
+ if ( pg->u.free.first_dirty == INVALID_DIRTY_IDX )
+ break;
+
+ for ( i = pg->u.free.first_dirty; i < (1U << order); i++)
+ {
+ if ( test_bit(_PGC_need_scrub, &pg[i].count_info) )
+ {
+ scrub_one_page(&pg[i]);
+ pg[i].count_info &= ~PGC_need_scrub;
+ node_need_scrub[node]--;
+ }
+ }
+
+ page_list_del(pg, &heap(node, zone, order));
+ page_list_add_scrub(pg, node, zone, order, INVALID_DIRTY_IDX);
+
+ if ( node_need_scrub[node] == 0 )
+ return;
+ }
+ } while ( order-- != 0 );
+ }
+}
+
/* Free 2^@order set of pages. */
static void free_heap_pages(
- struct page_info *pg, unsigned int order)
+ struct page_info *pg, unsigned int order, bool need_scrub)
{
unsigned long mask, mfn = page_to_mfn(pg);
unsigned int i, node = phys_to_nid(page_to_maddr(pg)), tainted = 0;
@@ -961,10 +1064,20 @@ static void free_heap_pages(
/* This page is not a guest frame any more. */
page_set_owner(&pg[i], NULL); /* set_gpfn_from_mfn snoops pg owner */
set_gpfn_from_mfn(mfn + i, INVALID_M2P_ENTRY);
+
+ if ( need_scrub )
+ pg[i].count_info |= PGC_need_scrub;
}
avail[node][zone] += 1 << order;
total_avail_pages += 1 << order;
+ if ( need_scrub )
+ {
+ node_need_scrub[node] += 1 << order;
+ pg->u.free.first_dirty = 0;
+ }
+ else
+ pg->u.free.first_dirty = INVALID_DIRTY_IDX;
if ( tmem_enabled() )
midsize_alloc_zone_pages = max(
@@ -977,35 +1090,53 @@ static void free_heap_pages(
if ( (page_to_mfn(pg) & mask) )
{
+ struct page_info *predecessor = pg - mask;
+
/* Merge with predecessor block? */
- if ( !mfn_valid(_mfn(page_to_mfn(pg-mask))) ||
- !page_state_is(pg-mask, free) ||
- (PFN_ORDER(pg-mask) != order) ||
- (phys_to_nid(page_to_maddr(pg-mask)) != node) )
+ if ( !mfn_valid(_mfn(page_to_mfn(predecessor))) ||
+ !page_state_is(predecessor, free) ||
+ (PFN_ORDER(predecessor) != order) ||
+ (phys_to_nid(page_to_maddr(predecessor)) != node) )
break;
- pg -= mask;
- page_list_del(pg, &heap(node, zone, order));
+
+ page_list_del(predecessor, &heap(node, zone, order));
+
+ if ( predecessor->u.free.first_dirty != INVALID_DIRTY_IDX )
+ need_scrub = true;
+ /* ... and keep predecessor's first_dirty. */
+ else if ( pg->u.free.first_dirty != INVALID_DIRTY_IDX )
+ predecessor->u.free.first_dirty = (1U << order) +
+ pg->u.free.first_dirty;
+
+ pg = predecessor;
}
else
{
+ struct page_info *successor = pg + mask;
+
/* Merge with successor block? */
- if ( !mfn_valid(_mfn(page_to_mfn(pg+mask))) ||
- !page_state_is(pg+mask, free) ||
- (PFN_ORDER(pg+mask) != order) ||
- (phys_to_nid(page_to_maddr(pg+mask)) != node) )
+ if ( !mfn_valid(_mfn(page_to_mfn(successor))) ||
+ !page_state_is(successor, free) ||
+ (PFN_ORDER(successor) != order) ||
+ (phys_to_nid(page_to_maddr(successor)) != node) )
break;
- page_list_del(pg + mask, &heap(node, zone, order));
+ page_list_del(successor, &heap(node, zone, order));
+
+ if ( successor->u.free.first_dirty != INVALID_DIRTY_IDX )
+ need_scrub = true;
}
order++;
}
- PFN_ORDER(pg) = order;
- page_list_add_tail(pg, &heap(node, zone, order));
+ page_list_add_scrub(pg, node, zone, order, pg->u.free.first_dirty);
if ( tainted )
reserve_offlined_page(pg);
+ if ( need_scrub )
+ scrub_free_pages(node);
+
spin_unlock(&heap_lock);
}
@@ -1226,7 +1357,7 @@ unsigned int online_page(unsigned long mfn, uint32_t
*status)
spin_unlock(&heap_lock);
if ( (y & PGC_state) == PGC_state_offlined )
- free_heap_pages(pg, 0);
+ free_heap_pages(pg, 0, false);
return ret;
}
@@ -1295,7 +1426,7 @@ static void init_heap_pages(
nr_pages -= n;
}
- free_heap_pages(pg+i, 0);
+ free_heap_pages(pg + i, 0, false);
}
}
@@ -1622,7 +1753,7 @@ void free_xenheap_pages(void *v, unsigned int order)
memguard_guard_range(v, 1 << (order + PAGE_SHIFT));
- free_heap_pages(virt_to_page(v), order);
+ free_heap_pages(virt_to_page(v), order, false);
}
#else
@@ -1676,12 +1807,9 @@ void free_xenheap_pages(void *v, unsigned int order)
pg = virt_to_page(v);
for ( i = 0; i < (1u << order); i++ )
- {
- scrub_one_page(&pg[i]);
pg[i].count_info &= ~PGC_xen_heap;
- }
- free_heap_pages(pg, order);
+ free_heap_pages(pg, order, true);
}
#endif
@@ -1790,7 +1918,7 @@ struct page_info *alloc_domheap_pages(
if ( d && !(memflags & MEMF_no_owner) &&
assign_pages(d, pg, order, memflags) )
{
- free_heap_pages(pg, order);
+ free_heap_pages(pg, order, false);
return NULL;
}
@@ -1858,11 +1986,7 @@ void free_domheap_pages(struct page_info *pg, unsigned
int order)
scrub = 1;
}
- if ( unlikely(scrub) )
- for ( i = 0; i < (1 << order); i++ )
- scrub_one_page(&pg[i]);
-
- free_heap_pages(pg, order);
+ free_heap_pages(pg, order, scrub);
}
if ( drop_dom_ref )
diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
index 13c673a..889a85e 100644
--- a/xen/include/asm-arm/mm.h
+++ b/xen/include/asm-arm/mm.h
@@ -44,7 +44,16 @@ struct page_info
/* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
struct {
/* Do TLBs need flushing for safety before next page use? */
- bool_t need_tlbflush;
+ unsigned long need_tlbflush:1;
+
+ /*
+ * Index of the first *possibly* unscrubbed page in the buddy.
+ * One more than maximum possible order (MAX_ORDER+1) to
+ * accommodate INVALID_DIRTY_IDX.
+ */
+#define INVALID_DIRTY_IDX (-1UL & (((1UL<<MAX_ORDER) + 2) - 1))
+ unsigned long first_dirty:MAX_ORDER + 2;
+
} free;
} u;
@@ -107,6 +116,13 @@ struct page_info
#define PGC_count_width PG_shift(9)
#define PGC_count_mask ((1UL<<PGC_count_width)-1)
+/*
+ * Page needs to be scrubbed. Since this bit can only be set on a page that is
+ * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
+ */
+#define _PGC_need_scrub _PGC_allocated
+#define PGC_need_scrub PGC_allocated
+
extern unsigned long xenheap_mfn_start, xenheap_mfn_end;
extern vaddr_t xenheap_virt_end;
#ifdef CONFIG_ARM_64
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index d33599d..cd00bef 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -88,7 +88,15 @@ struct page_info
/* Page is on a free list: ((count_info & PGC_count_mask) == 0). */
struct {
/* Do TLBs need flushing for safety before next page use? */
- bool_t need_tlbflush;
+ unsigned long need_tlbflush:1;
+
+ /*
+ * Index of the first *possibly* unscrubbed page in the buddy.
+ * One more than maximum possible order (MAX_ORDER+1) to
+ * accommodate INVALID_DIRTY_IDX.
+ */
+#define INVALID_DIRTY_IDX (-1UL & (((1UL<<MAX_ORDER) + 2) - 1))
+ unsigned long first_dirty:MAX_ORDER + 2;
} free;
} u;
@@ -233,6 +241,13 @@ struct page_info
#define PGC_count_width PG_shift(9)
#define PGC_count_mask ((1UL<<PGC_count_width)-1)
+/*
+ * Page needs to be scrubbed. Since this bit can only be set on a page that is
+ * free (i.e. in PGC_state_free) we can reuse PGC_allocated bit.
+ */
+#define _PGC_need_scrub _PGC_allocated
+#define PGC_need_scrub PGC_allocated
+
struct spage_info
{
unsigned long type_info;
--
1.8.3.1
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