Hi Roman,
On Tue, Dec 15, 2020 at 11:36:15AM -0800, Roman Gushchin wrote:
> Currently cma areas without a fixed base address are allocated
> close to the end of the node. This placement is sub-optimal because
> of how the compaction works: it effectively moves pages into
> the cma area. In particular, it often brings in hot executable pages,
> even if there is a plenty of free memory on the machine.
> This results in more cma allocation failures.
>
> Instead let's place cma areas close to the beginning of a node.
> Cma first tries to start with highmem_start, so we shouldn't mess
> up with DMA32. In this case the compaction will help to free cma
> areas, resulting in better cma allocation success rates.
>
> Signed-off-by: Roman Gushchin <[email protected]>
> ---
> include/linux/memblock.h | 5 +++--
> mm/cma.c | 4 ++--
> mm/memblock.c | 26 +++++++++++++++-----------
> 3 files changed, 20 insertions(+), 15 deletions(-)
>
> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
> index 9c5cc95c7cee..698188066450 100644
> --- a/include/linux/memblock.h
> +++ b/include/linux/memblock.h
> @@ -384,8 +384,9 @@ static inline int memblock_get_region_node(const struct
> memblock_region *r)
> phys_addr_t memblock_phys_alloc_range(phys_addr_t size, phys_addr_t align,
> phys_addr_t start, phys_addr_t end);
> phys_addr_t memblock_alloc_range_nid(phys_addr_t size,
> - phys_addr_t align, phys_addr_t start,
> - phys_addr_t end, int nid, bool exact_nid);
> + phys_addr_t align, phys_addr_t start,
> + phys_addr_t end, int nid, bool exact_nid,
> + bool bottom_up);
> phys_addr_t memblock_phys_alloc_try_nid(phys_addr_t size, phys_addr_t align,
> int nid);
>
> static inline phys_addr_t memblock_phys_alloc(phys_addr_t size,
> diff --git a/mm/cma.c b/mm/cma.c
> index 20c4f6f40037..1b42be6d059b 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -332,13 +332,13 @@ int __init cma_declare_contiguous_nid(phys_addr_t base,
> */
> if (base < highmem_start && limit > highmem_start) {
> addr = memblock_alloc_range_nid(size, alignment,
> - highmem_start, limit, nid, true);
> + highmem_start, limit, nid, true, true);
> limit = highmem_start;
> }
>
> if (!addr) {
> addr = memblock_alloc_range_nid(size, alignment, base,
> - limit, nid, true);
> + limit, nid, true, true);
> if (!addr) {
> ret = -ENOMEM;
> goto err;
> diff --git a/mm/memblock.c b/mm/memblock.c
> index b8b7be0561c4..c334b401fe16 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -272,6 +272,7 @@ __memblock_find_range_top_down(phys_addr_t start,
> phys_addr_t end,
> * %MEMBLOCK_ALLOC_ACCESSIBLE
> * @nid: nid of the free area to find, %NUMA_NO_NODE for any node
> * @flags: pick from blocks based on memory attributes
> + * @bottom_up: force bottom-up allocation
Why wouldn't you use memblock_set_bottom_up() around the allocations in
CMA, e.g.
bool bottom_up = memblock_bottom_up();
if (!bottom_up)
memblock_set_bottom_up(true);
/* allocate memory */
memblock_set_bottom_up(bottom_up);
> *
> * Find @size free area aligned to @align in the specified range and node.
> *
> @@ -289,7 +290,8 @@ __memblock_find_range_top_down(phys_addr_t start,
> phys_addr_t end,
--
Sincerely yours,
Mike.
