From: Uladzislau Rezki <uladzislau.rezki@xxxxxxxx> Subject: mm/vmalloc: add adjust_search_size parameter 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. Link: https://lkml.kernel.org/r/20220119143540.601149-2-urezki@xxxxxxxxx Signed-off-by: Uladzislau Rezki <uladzislau.rezki@xxxxxxxx> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx> Cc: Christoph Hellwig <hch@xxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Nicholas Piggin <npiggin@xxxxxxxxx> Cc: Oleksiy Avramchenko <oleksiy.avramchenko@xxxxxxxxxxxxxx> Cc: Vasily Averin <vvs@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/vmalloc.c | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) --- a/mm/vmalloc.c~mm-vmalloc-add-adjust_search_size-parameter +++ a/mm/vmalloc.c @@ -1189,22 +1189,28 @@ is_within_this_va(struct vmap_area *va, /* * 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 { @@ -1214,9 +1220,9 @@ find_vmap_lowest_match(unsigned long siz /* * 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; } @@ -1232,7 +1238,7 @@ find_vmap_lowest_match(unsigned long siz 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 @@ -1280,7 +1286,7 @@ find_vmap_lowest_match_check(unsigned lo 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) @@ -1431,12 +1437,25 @@ 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; _
