[Xen-devel] [PATCH 7 of 9] x86/mm: Fix paging stats

[Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>]

 xen/arch/x86/mm/mem_sharing.c |   6 +++++-
 xen/arch/x86/mm/p2m.c         |  12 +++++++++++-
 xen/common/memory.c           |   2 +-
 xen/include/asm-x86/p2m.h     |   6 ++++--
 4 files changed, 21 insertions(+), 5 deletions(-)


There are several corner cases in which a page is paged back in, not by paging,
and the stats are not properly updated.

Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>

diff -r 75dec1a0ba2d -r 244804e8a002 xen/arch/x86/mm/mem_sharing.c
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -881,8 +881,12 @@ int mem_sharing_add_to_physmap(struct do
         ret = -ENOENT;
         mem_sharing_gfn_destroy(cd, gfn_info);
         put_page_and_type(spage);
-    } else
+    } else {
         ret = 0;
+        /* There is a chance we're plugging a hole where a paged out page was 
*/
+        if ( p2m_is_paging(cmfn_type) && (cmfn_type != p2m_ram_paging_out) )
+            atomic_dec(&cd->paged_pages);
+    }
 
     atomic_inc(&nr_saved_mfns);
 
diff -r 75dec1a0ba2d -r 244804e8a002 xen/arch/x86/mm/p2m.c
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -510,6 +510,11 @@ guest_physmap_add_entry(struct domain *d
             /* Count how man PoD entries we'll be replacing if successful */
             pod_count++;
         }
+        else if ( p2m_is_paging(ot) && (ot != p2m_ram_paging_out) )
+        {
+            /* We're plugging a hole in the physmap where a paged out page was 
*/
+            atomic_dec(&d->paged_pages);
+        }
     }
 
     /* Then, look for m->p mappings for this range and deal with them */
@@ -878,7 +883,8 @@ int p2m_mem_paging_evict(struct domain *
  * released by the guest. The pager is supposed to drop its reference of the
  * gfn.
  */
-void p2m_mem_paging_drop_page(struct domain *d, unsigned long gfn)
+void p2m_mem_paging_drop_page(struct domain *d, unsigned long gfn,
+                                p2m_type_t p2mt)
 {
     mem_event_request_t req;
 
@@ -897,6 +903,10 @@ void p2m_mem_paging_drop_page(struct dom
     req.flags = MEM_EVENT_FLAG_DROP_PAGE;
 
     mem_event_put_request(d, &d->mem_event->paging, &req);
+
+    /* Update stats unless the page hasn't yet been evicted */
+    if ( p2mt != p2m_ram_paging_out )
+        atomic_dec(&d->paged_pages);
 }
 
 /**
diff -r 75dec1a0ba2d -r 244804e8a002 xen/common/memory.c
--- a/xen/common/memory.c
+++ b/xen/common/memory.c
@@ -166,7 +166,7 @@ int guest_remove_page(struct domain *d, 
     if ( unlikely(p2m_is_paging(p2mt)) )
     {
         guest_physmap_remove_page(d, gmfn, mfn, 0);
-        p2m_mem_paging_drop_page(d, gmfn);
+        p2m_mem_paging_drop_page(d, gmfn, p2mt);
         put_gfn(d, gmfn);
         return 1;
     }
diff -r 75dec1a0ba2d -r 244804e8a002 xen/include/asm-x86/p2m.h
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -566,7 +566,8 @@ int p2m_mem_paging_nominate(struct domai
 /* Evict a frame */
 int p2m_mem_paging_evict(struct domain *d, unsigned long gfn);
 /* Tell xenpaging to drop a paged out frame */
-void p2m_mem_paging_drop_page(struct domain *d, unsigned long gfn);
+void p2m_mem_paging_drop_page(struct domain *d, unsigned long gfn, 
+                                p2m_type_t p2mt);
 /* Start populating a paged out frame */
 void p2m_mem_paging_populate(struct domain *d, unsigned long gfn);
 /* Prepare the p2m for paging a frame in */
@@ -574,7 +575,8 @@ int p2m_mem_paging_prep(struct domain *d
 /* Resume normal operation (in case a domain was paused) */
 void p2m_mem_paging_resume(struct domain *d);
 #else
-static inline void p2m_mem_paging_drop_page(struct domain *d, unsigned long 
gfn)
+static inline void p2m_mem_paging_drop_page(struct domain *d, unsigned long 
gfn,
+                                            p2m_type_t p2mt)
 { }
 static inline void p2m_mem_paging_populate(struct domain *d, unsigned long gfn)
 { }

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