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memory: merge adjacent segments of a single memory region

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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;
}