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authorAvi Kivity <avi@redhat.com>2012-02-13 20:45:32 +0200
committerAvi Kivity <avi@redhat.com>2012-02-29 13:44:45 +0200
commit07f07b31e57efa6e4f563802136ffa1694a2692b (patch)
tree08279523676b35f6ab07c76d0c5914fcdec8d45b
parentc19e8800d4a9c019299cc9232b4e628469a81d2d (diff)
memory: allow phys_map tree paths to terminate early
When storing large contiguous ranges in phys_map, all values tend to be the same pointers to a single MemoryRegionSection. Collapse them by marking nodes with level > 0 as leaves. This reduces tree memory usage dramatically. Signed-off-by: Avi Kivity <avi@redhat.com>
-rw-r--r--exec.c28
1 files changed, 17 insertions, 11 deletions
diff --git a/exec.c b/exec.c
index a2015f7..0c93b26 100644
--- a/exec.c
+++ b/exec.c
@@ -193,19 +193,20 @@ static unsigned phys_sections_nb, phys_sections_nb_alloc;
static uint16_t phys_section_unassigned;
struct PhysPageEntry {
- /* index into phys_sections (last level) or phys_map_nodes (others) */
- uint16_t ptr;
+ uint16_t is_leaf : 1;
+ /* index into phys_sections (is_leaf) or phys_map_nodes (!is_leaf) */
+ uint16_t ptr : 15;
};
/* Simple allocator for PhysPageEntry nodes */
static PhysPageEntry (*phys_map_nodes)[L2_SIZE];
static unsigned phys_map_nodes_nb, phys_map_nodes_nb_alloc;
-#define PHYS_MAP_NODE_NIL ((uint16_t)~0)
+#define PHYS_MAP_NODE_NIL (((uint16_t)~0) >> 1)
/* This is a multi-level map on the physical address space.
The bottom level has pointers to MemoryRegionSections. */
-static PhysPageEntry phys_map = { .ptr = PHYS_MAP_NODE_NIL };
+static PhysPageEntry phys_map = { .ptr = PHYS_MAP_NODE_NIL, .is_leaf = 0 };
static void io_mem_init(void);
static void memory_map_init(void);
@@ -423,6 +424,7 @@ static uint16_t phys_map_node_alloc(void)
assert(ret != PHYS_MAP_NODE_NIL);
assert(ret != phys_map_nodes_nb_alloc);
for (i = 0; i < L2_SIZE; ++i) {
+ phys_map_nodes[ret][i].is_leaf = 0;
phys_map_nodes[ret][i].ptr = PHYS_MAP_NODE_NIL;
}
return ret;
@@ -440,12 +442,14 @@ static void phys_page_set_level(PhysPageEntry *lp, target_phys_addr_t *index,
{
PhysPageEntry *p;
int i;
+ target_phys_addr_t step = (target_phys_addr_t)1 << (level * L2_BITS);
- if (lp->ptr == PHYS_MAP_NODE_NIL) {
+ if (!lp->is_leaf && lp->ptr == PHYS_MAP_NODE_NIL) {
lp->ptr = phys_map_node_alloc();
p = phys_map_nodes[lp->ptr];
if (level == 0) {
for (i = 0; i < L2_SIZE; i++) {
+ p[i].is_leaf = 1;
p[i].ptr = phys_section_unassigned;
}
}
@@ -455,10 +459,11 @@ static void phys_page_set_level(PhysPageEntry *lp, target_phys_addr_t *index,
lp = &p[(*index >> (level * L2_BITS)) & (L2_SIZE - 1)];
while (*nb && lp < &p[L2_SIZE]) {
- if (level == 0) {
+ if ((*index & (step - 1)) == 0 && *nb >= step) {
+ lp->is_leaf = true;
lp->ptr = leaf;
- ++*index;
- --*nb;
+ *index += step;
+ *nb -= step;
} else {
phys_page_set_level(lp, index, nb, leaf, level - 1);
}
@@ -470,7 +475,7 @@ static void phys_page_set(target_phys_addr_t index, target_phys_addr_t nb,
uint16_t leaf)
{
/* Wildly overreserve - it doesn't matter much. */
- phys_map_node_reserve((nb + L2_SIZE - 1) / L2_SIZE * P_L2_LEVELS);
+ phys_map_node_reserve(3 * P_L2_LEVELS);
phys_page_set_level(&phys_map, &index, &nb, leaf, P_L2_LEVELS - 1);
}
@@ -484,7 +489,7 @@ static MemoryRegionSection phys_page_find(target_phys_addr_t index)
target_phys_addr_t delta;
uint16_t s_index = phys_section_unassigned;
- for (i = P_L2_LEVELS - 1; i >= 0; i--) {
+ for (i = P_L2_LEVELS - 1; i >= 0 && !lp.is_leaf; i--) {
if (lp.ptr == PHYS_MAP_NODE_NIL) {
goto not_found;
}
@@ -2580,12 +2585,13 @@ static void destroy_l2_mapping(PhysPageEntry *lp, unsigned level)
p = phys_map_nodes[lp->ptr];
for (i = 0; i < L2_SIZE; ++i) {
- if (level > 0) {
+ if (!p[i].is_leaf) {
destroy_l2_mapping(&p[i], level - 1);
} else {
destroy_page_desc(p[i].ptr);
}
}
+ lp->is_leaf = 0;
lp->ptr = PHYS_MAP_NODE_NIL;
}