From: Uladzislau Rezki <uladzislau.rezki@xxxxxxxx>
Extend the find_vmap_lowest_match() function with one more
parameter. It is "adjust_search_size" boolean variable, so
it is possible to control an accuracy of search block if a
specific alignment is required.
With this patch, a search size is always adjusted, to serve
a request as fast as possible because of performance reason.
But there is one exception though, it is short ranges where
requested size corresponds to passed vstart/vend restriction
together with a specific alignment request. In such scenario
an adjustment wold not lead to success allocation.
Signed-off-by: Uladzislau Rezki <uladzislau.rezki@xxxxxxxx>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
---
mm/vmalloc.c | 37 ++++++++++++++++++++++++++++---------
1 file changed, 28 insertions(+), 9 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index ed0f9eaa61a9..52ee67107046 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1192,22 +1192,28 @@ is_within_this_va(struct vmap_area *va, unsigned long size,
/*
* Find the first free block(lowest start address) in the tree,
* that will accomplish the request corresponding to passing
- * parameters.
+ * parameters. Please note, with an alignment bigger than PAGE_SIZE,
+ * a search length is adjusted to account for worst case alignment
+ * overhead.
*/
static __always_inline struct vmap_area *
-find_vmap_lowest_match(unsigned long size,
- unsigned long align, unsigned long vstart)
+find_vmap_lowest_match(unsigned long size, unsigned long align,
+ unsigned long vstart, bool adjust_search_size)
{
struct vmap_area *va;
struct rb_node *node;
+ unsigned long length;
/* Start from the root. */
node = free_vmap_area_root.rb_node;
+ /* Adjust the search size for alignment overhead. */
+ length = adjust_search_size ? size + align - 1 : size;
+
while (node) {
va = rb_entry(node, struct vmap_area, rb_node);
- if (get_subtree_max_size(node->rb_left) >= size &&
+ if (get_subtree_max_size(node->rb_left) >= length &&
vstart < va->va_start) {
node = node->rb_left;
} else {
@@ -1217,9 +1223,9 @@ find_vmap_lowest_match(unsigned long size,
/*
* Does not make sense to go deeper towards the right
* sub-tree if it does not have a free block that is
- * equal or bigger to the requested search size.
+ * equal or bigger to the requested search length.
*/
- if (get_subtree_max_size(node->rb_right) >= size) {
+ if (get_subtree_max_size(node->rb_right) >= length) {
node = node->rb_right;
continue;
}
@@ -1235,7 +1241,7 @@ find_vmap_lowest_match(unsigned long size,
if (is_within_this_va(va, size, align, vstart))
return va;
- if (get_subtree_max_size(node->rb_right) >= size &&
+ if (get_subtree_max_size(node->rb_right) >= length &&
vstart <= va->va_start) {
/*
* Shift the vstart forward. Please note, we update it with
@@ -1283,7 +1289,7 @@ find_vmap_lowest_match_check(unsigned long size, unsigned long align)
get_random_bytes(&rnd, sizeof(rnd));
vstart = VMALLOC_START + rnd;
- va_1 = find_vmap_lowest_match(size, align, vstart);
+ va_1 = find_vmap_lowest_match(size, align, vstart, false);
va_2 = find_vmap_lowest_linear_match(size, align, vstart);
if (va_1 != va_2)
@@ -1434,12 +1440,25 @@ static __always_inline unsigned long
__alloc_vmap_area(unsigned long size, unsigned long align,
unsigned long vstart, unsigned long vend)
{
+ bool adjust_search_size = true;
unsigned long nva_start_addr;
struct vmap_area *va;
enum fit_type type;
int ret;
- va = find_vmap_lowest_match(size, align, vstart);
+ /*
+ * Do not adjust when:
+ * a) align <= PAGE_SIZE, because it does not make any sense.
+ * All blocks(their start addresses) are at least PAGE_SIZE
+ * aligned anyway;
+ * b) a short range where a requested size corresponds to exactly
+ * specified [vstart:vend] interval and an alignment > PAGE_SIZE.
+ * With adjusted search length an allocation would not succeed.
+ */
+ if (align <= PAGE_SIZE || (align > PAGE_SIZE && (vend - vstart) == size))
+ adjust_search_size = false;
+
+ va = find_vmap_lowest_match(size, align, vstart, adjust_search_size);
if (unlikely(!va))
return vend;
--
2.30.2
