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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v7 2/9] 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 v7
* Simplified tracking dirty pages in reserve_offlined_page() to match how
it is done in alloc_heap_pages()
* Changed page_info.u.free.need_tlbflush definition to bool:1
* Added BUILD_BUG_ON() to make sure page_info.u stays within unsigned long
xen/common/page_alloc.c | 157 ++++++++++++++++++++++++++++++++++++++++-------
xen/include/asm-arm/mm.h | 18 +++++-
xen/include/asm-x86/mm.h | 17 ++++-
3 files changed, 167 insertions(+), 25 deletions(-)
diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 330f8ed..b857a44 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;
@@ -678,13 +680,30 @@ 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 )
+ {
+ ASSERT(first_dirty < (1U << order));
+ 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,
unsigned int order, unsigned int memflags,
struct domain *d)
{
- unsigned int i, j, zone = 0, nodemask_retry = 0;
+ unsigned int i, j, zone = 0, nodemask_retry = 0, first_dirty;
nodeid_t first_node, node = MEMF_get_node(memflags), req_node = node;
unsigned long request = 1UL << order;
struct page_info *pg;
@@ -798,12 +817,26 @@ static struct page_info *alloc_heap_pages(
return NULL;
found:
+
+ first_dirty = 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));
- pg += 1 << j;
+ j--;
+ page_list_add_scrub(pg, node, zone, j,
+ (1U << j) > first_dirty ?
+ first_dirty : INVALID_DIRTY_IDX);
+ pg += 1U << j;
+
+ if ( first_dirty != INVALID_DIRTY_IDX )
+ {
+ /* Adjust first_dirty */
+ if ( first_dirty >= 1U << j )
+ first_dirty -= 1U << j;
+ else
+ first_dirty = 0; /* We've moved past original first_dirty */
+ }
}
ASSERT(avail[node][zone] >= request);
@@ -850,12 +883,20 @@ 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;
- int cur_order;
+ unsigned int cur_order, first_dirty;
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.
+ */
+ first_dirty = 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)) )
@@ -866,6 +907,8 @@ static int reserve_offlined_page(struct page_info *head)
if ( page_state_is(cur_head, offlined) )
{
cur_head++;
+ if ( first_dirty != INVALID_DIRTY_IDX && first_dirty )
+ first_dirty--;
continue;
}
@@ -892,9 +935,20 @@ 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;
+ page_list_add_scrub(cur_head, node, zone, cur_order,
+ (1U << cur_order) > first_dirty ?
+ first_dirty : INVALID_DIRTY_IDX);
cur_head += (1 << cur_order);
+
+ /* Adjust first_dirty if needed. */
+ if ( first_dirty != INVALID_DIRTY_IDX )
+ {
+ if ( first_dirty >= 1U << cur_order )
+ first_dirty -= 1U << cur_order;
+ else
+ first_dirty = 0;
+ }
+
break;
}
}
@@ -919,9 +973,53 @@ 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 +1059,20 @@ 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(
@@ -988,6 +1096,12 @@ static void free_heap_pages(
page_list_del(predecessor, &heap(node, zone, order));
+ /* Keep predecessor's first_dirty if it is already set. */
+ if ( predecessor->u.free.first_dirty == INVALID_DIRTY_IDX &&
+ pg->u.free.first_dirty != INVALID_DIRTY_IDX )
+ predecessor->u.free.first_dirty = (1U << order) +
+ pg->u.free.first_dirty;
+
pg = predecessor;
}
else
@@ -1007,12 +1121,14 @@ static void free_heap_pages(
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);
}
@@ -1233,7 +1349,7 @@ 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;
}
@@ -1276,6 +1392,8 @@ static void init_heap_pages(
{
unsigned long i;
+ BUILD_BUG_ON(sizeof(pg->u) != sizeof(unsigned long));
+
for ( i = 0; i < nr_pages; i++ )
{
unsigned int nid = phys_to_nid(page_to_maddr(pg+i));
@@ -1302,7 +1420,7 @@ static void init_heap_pages(
nr_pages -= n;
}
- free_heap_pages(pg+i, 0);
+ free_heap_pages(pg + i, 0, false);
}
}
@@ -1629,7 +1747,7 @@ 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
@@ -1683,12 +1801,9 @@ 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
@@ -1797,7 +1912,7 @@ 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;
}
@@ -1865,11 +1980,7 @@ 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 ef84b72..572337c 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;
+ bool need_tlbflush:1;
+
+ /*
+ * Index of the first *possibly* unscrubbed page in the buddy.
+ * One more bit than maximum possible order to accommodate
+ * INVALID_DIRTY_IDX.
+ */
+#define INVALID_DIRTY_IDX ((1UL << (MAX_ORDER + 1)) - 1)
+ unsigned long first_dirty:MAX_ORDER + 1;
+
} 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 mfn_t 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 2bf3f33..07dc963 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;
+ bool need_tlbflush:1;
+
+ /*
+ * Index of the first *possibly* unscrubbed page in the buddy.
+ * One more bit than maximum possible order to accommodate
+ * INVALID_DIRTY_IDX.
+ */
+#define INVALID_DIRTY_IDX ((1UL << (MAX_ORDER + 1)) - 1)
+ unsigned long first_dirty:MAX_ORDER + 1;
} 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
+
#define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
#define is_xen_heap_mfn(mfn) \
(__mfn_valid(mfn) && is_xen_heap_page(__mfn_to_page(mfn)))
--
1.8.3.1
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