[Xen-devel] [PATCH RFC 2/8] mm: Place unscrubbed pages at the end of pagelist

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

. so that it's easy to find pages that need to be scrubbed (those pages are
now marked with _PGC_need_scrub bit).

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 xen/common/page_alloc.c  |   97 +++++++++++++++++++++++++++++++++++----------
 xen/include/asm-x86/mm.h |    4 ++
 2 files changed, 79 insertions(+), 22 deletions(-)

diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
index 352eba9..653bb91 100644
--- a/xen/common/page_alloc.c
+++ b/xen/common/page_alloc.c
@@ -385,6 +385,8 @@ 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 node_need_scrub[MAX_NUMNODES];
+
 static unsigned long *avail[MAX_NUMNODES];
 static long total_avail_pages;
 
@@ -809,7 +811,7 @@ static struct page_info *alloc_heap_pages(
     while ( j != order )
     {
         PFN_ORDER(pg) = --j;
-        page_list_add_tail(pg, &heap(node, zone, j));
+        page_list_add(pg, &heap(node, zone, j));
         pg += 1 << j;
     }
 
@@ -829,6 +831,8 @@ static struct page_info *alloc_heap_pages(
         BUG_ON(pg[i].count_info != PGC_state_free);
         pg[i].count_info = PGC_state_inuse;
 
+        BUG_ON(test_bit(_PGC_need_scrub, &pg[i].count_info));
+
         if ( !(memflags & MEMF_no_tlbflush) )
             accumulate_tlbflush(&need_tlbflush, &pg[i],
                                 &tlbflush_timestamp);
@@ -899,7 +903,10 @@ 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));
+                if ( test_bit(_PGC_need_scrub, &cur_head->count_info) )
+                    page_list_add_tail(cur_head, &heap(node, zone, cur_order));
+                else
+                    page_list_add(cur_head, &heap(node, zone, cur_order));
                 PFN_ORDER(cur_head) = cur_order;
                 cur_head += (1 << cur_order);
                 break;
@@ -927,7 +934,7 @@ static int reserve_offlined_page(struct page_info *head)
 }
 
 static bool_t can_merge(struct page_info *head, unsigned int node,
-                        unsigned int order)
+                        unsigned int order, bool_t need_scrub)
 {
     if  ( !mfn_valid(page_to_mfn(head)) ||
           !page_state_is(head, free) ||
@@ -935,11 +942,16 @@ static bool_t can_merge(struct page_info *head, unsigned 
int node,
           (phys_to_nid(page_to_maddr(head)) != node) )
         return 0;
 
+    if ( !!need_scrub ^
+         !!test_bit(_PGC_need_scrub, &head->count_info) )
+        return 0;
+
     return 1;
 }
 
 static void merge_chunks(struct page_info *pg, unsigned int node,
-                         unsigned int zone, unsigned int order)
+                         unsigned int zone, unsigned int order,
+                         bool_t need_scrub)
 {
     ASSERT(spin_is_locked(&heap_lock));
 
@@ -951,7 +963,7 @@ static void merge_chunks(struct page_info *pg, unsigned int 
node,
         if ( (page_to_mfn(pg) & mask) )
         {
             /* Merge with predecessor block? */
-            if ( !can_merge(pg - mask, node, order) )
+            if ( !can_merge(pg - mask, node, order, need_scrub) )
                 break;
 
             pg -= mask;
@@ -960,7 +972,7 @@ static void merge_chunks(struct page_info *pg, unsigned int 
node,
         else
         {
             /* Merge with successor block? */
-            if ( !can_merge(pg + mask, node, order) )
+            if ( !can_merge(pg + mask, node, order, need_scrub) )
                 break;
 
             page_list_del(pg + mask, &heap(node, zone, order));
@@ -970,12 +982,49 @@ static void merge_chunks(struct page_info *pg, unsigned 
int node,
     }
 
     PFN_ORDER(pg) = order;
-    page_list_add_tail(pg, &heap(node, zone, order));
+    if ( need_scrub )
+        page_list_add_tail(pg, &heap(node, zone, order));
+    else
+        page_list_add(pg, &heap(node, zone, order));
+}
+
+static void scrub_free_pages(unsigned int node)
+{
+    struct page_info *pg;
+    unsigned int i, zone;
+    int order;
+
+    ASSERT(spin_is_locked(&heap_lock));
+
+    if ( !node_need_scrub[node] )
+        return;
+
+    for ( zone = 0; zone < NR_ZONES; zone++ )
+    {
+        for ( order = MAX_ORDER; order >= 0; order-- )
+        {
+            while ( !page_list_empty(&heap(node, zone, order)) )
+            {
+                /* Unscrubbed pages are always at the end of the list. */
+                pg = page_list_last(&heap(node, zone, order));
+                if ( !test_bit(_PGC_need_scrub, &pg[0].count_info) )
+                    break;
+
+                for ( i = 0; i < (1 << order); i++)
+                {
+                    scrub_one_page(&pg[i]);
+                    pg[i].count_info &= ~PGC_need_scrub;
+                }
+
+                node_need_scrub[node] -= (1 << order);
+            }
+        }
+    }
 }
 
 /* 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_t need_scrub)
 {
     unsigned long mfn = page_to_mfn(pg);
     unsigned int i, node = phys_to_nid(page_to_maddr(pg)), tainted = 0;
@@ -1024,11 +1073,22 @@ static void free_heap_pages(
         midsize_alloc_zone_pages = max(
             midsize_alloc_zone_pages, total_avail_pages / MIDSIZE_ALLOC_FRAC);
 
-    merge_chunks(pg, node, zone, order);
+    if ( need_scrub && !tainted )
+    {
+        for ( i = 0; i < (1 << order); i++ )
+            pg[i].count_info |= PGC_need_scrub;
+
+        node_need_scrub[node] += (1 << order);
+    }
+
+    merge_chunks(pg, node, zone, order, need_scrub);
 
     if ( tainted )
         reserve_offlined_page(pg);
 
+    if ( need_scrub )
+        scrub_free_pages(node);
+
     spin_unlock(&heap_lock);
 }
 
@@ -1249,7 +1309,7 @@ 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, 0);
 
     return ret;
 }
@@ -1318,7 +1378,7 @@ static void init_heap_pages(
             nr_pages -= n;
         }
 
-        free_heap_pages(pg+i, 0);
+        free_heap_pages(pg + i, 0, 0);
     }
 }
 
@@ -1645,7 +1705,7 @@ 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, 0);
 }
 
 #else
@@ -1699,12 +1759,9 @@ 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, 1);
 }
 
 #endif
@@ -1813,7 +1870,7 @@ 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, 0);
         return NULL;
     }
     
@@ -1881,11 +1938,7 @@ 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-x86/mm.h b/xen/include/asm-x86/mm.h
index a66d5b1..b11124f 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -233,6 +233,10 @@ struct page_info
 #define PGC_count_width   PG_shift(9)
 #define PGC_count_mask    ((1UL<<PGC_count_width)-1)
 
+/* Page needs to be scrubbed */
+#define _PGC_need_scrub   PG_shift(10)
+#define PGC_need_scrub    PG_mask(1, 10)
+
 struct spage_info
 {
        unsigned long type_info;
-- 
1.7.1


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