mapcache: remember the last page address rather then the last address_index

A single address_index corresponds to multiple pages that might or
might not be mapped.  It is better to just remember the last page
address for the sake of this optimization, so that we are sure that it
is mapped.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

diff --git a/hw/xen_machine_fv.c b/hw/xen_machine_fv.c
index a353ee6cafc0a5dab99d40f5bc2ce25a977667ff..603a5083634bf5bdec6a108d860f3ec4f6fd99a0 100644 (file)
--- a/hw/xen_machine_fv.c
+++ b/hw/xen_machine_fv.c
@@ -63,7 +63,7 @@ static unsigned long nr_buckets;
 TAILQ_HEAD(map_cache_head, map_cache_rev) locked_entries = TAILQ_HEAD_INITIALIZER(locked_entries);
 
 /* For most cases (>99.9%), the page address is the same. */
-static unsigned long last_address_index = ~0UL;
+static unsigned long last_address_page = ~0UL;
 static uint8_t      *last_address_vaddr;
 
 static int qemu_map_cache_init(void)
@@ -138,7 +138,7 @@ uint8_t *qemu_map_cache(target_phys_addr_t phys_addr, uint8_t lock)
     unsigned long address_index  = phys_addr >> MCACHE_BUCKET_SHIFT;
     unsigned long address_offset = phys_addr & (MCACHE_BUCKET_SIZE-1);
 
-    if (address_index == last_address_index && !lock)
+    if ((phys_addr >> XC_PAGE_SHIFT) == last_address_page && !lock)
         return last_address_vaddr + address_offset;
 
     entry = &mapcache_entry[address_index % nr_buckets];
@@ -157,17 +157,17 @@ uint8_t *qemu_map_cache(target_phys_addr_t phys_addr, uint8_t lock)
     }
 
     if (!test_bit(address_offset>>XC_PAGE_SHIFT, entry->valid_mapping)) {
-        last_address_index = ~0UL;
+        last_address_page = ~0UL;
         return NULL;
     }
 
-    last_address_index = address_index;
+    last_address_page = phys_addr >> XC_PAGE_SHIFT;
     last_address_vaddr = entry->vaddr_base;
     if (lock) {
         struct map_cache_rev *reventry = qemu_mallocz(sizeof(struct map_cache_rev));
         entry->lock++;
         reventry->vaddr_req = last_address_vaddr + address_offset;
-        reventry->paddr_index = last_address_index;
+        reventry->paddr_index = address_index;
         TAILQ_INSERT_TAIL(&locked_entries, reventry, next);
     }
 
@@ -182,7 +182,7 @@ void qemu_invalidate_entry(uint8_t *buffer)
     int found = 0;
     
     if (last_address_vaddr == buffer)
-        last_address_index =  ~0UL;
+        last_address_page =  ~0UL;
 
     TAILQ_FOREACH(reventry, &locked_entries, next) {
         if (reventry->vaddr_req == buffer) {
@@ -252,7 +252,7 @@ void qemu_invalidate_map_cache(void)
         entry->vaddr_base  = NULL;
     }
 
-    last_address_index =  ~0UL;
+    last_address_page =  ~0UL;
     last_address_vaddr = NULL;
 
     mapcache_unlock();