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memory: merge adjacent segments of a single memory region 

Simple implementations of memory routers, for example the Cirrus VGA memory banks
or the 440FX PAM registers can generate adjacent memory regions which are contiguous.
Detect these and merge them; this saves kvm memory slots and shortens lookup times.

Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Avi Kivity 2011-07-26 14:26:03 +03:00 committed by Anthony Liguori
parent 5a58334769
commit 3d8e6bf977
1 changed files with 29 additions and 0 deletions
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29
memory.c
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@ -122,6 +122,34 @@ static void flatview_destroy(FlatView *view)
qemu_free(view->ranges);
}
static bool can_merge(FlatRange *r1, FlatRange *r2)
{
return addrrange_end(r1->addr) == r2->addr.start
&& r1->mr == r2->mr
&& r1->offset_in_region + r1->addr.size == r2->offset_in_region
&& r1->dirty_log_mask == r2->dirty_log_mask;
}
/* Attempt to simplify a view by merging ajacent ranges */
static void flatview_simplify(FlatView *view)
{
unsigned i, j;
i = 0;
while (i < view->nr) {
j = i + 1;
while (j < view->nr
&& can_merge(&view->ranges[j-1], &view->ranges[j])) {
view->ranges[i].addr.size += view->ranges[j].addr.size;
++j;
}
++i;
memmove(&view->ranges[i], &view->ranges[j],
(view->nr - j) * sizeof(view->ranges[j]));
view->nr -= j - i;
}
}
/* Render a memory region into the global view. Ranges in @view obscure
* ranges in @mr.
*/
@ -209,6 +237,7 @@ static FlatView generate_memory_topology(MemoryRegion *mr)
flatview_init(&view);
render_memory_region(&view, mr, 0, addrrange_make(0, UINT64_MAX));
flatview_simplify(&view);
return view;
}