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Date: Wed, 16 Dec 2020 17:07:04 +0200
From: Mike Rapoport <rppt@...nel.org>
To: Roman Gushchin <guro@...com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Rik van Riel <riel@...riel.com>,
Michal Hocko <mhocko@...nel.org>, linux-kernel@...r.kernel.org,
kernel-team@...com
Subject: Re: [PATCH] mm: cma: allocate cma areas bottom-up
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.
Sorry, I've missed this previously, but cma actually requires that
allocation will be below high_memory, so simply forcing memblock to
bottom_up mode will mess 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 <guro@...com>
> ---
> 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
> *
> * 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,
> static phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
> phys_addr_t align, phys_addr_t start,
> phys_addr_t end, int nid,
> - enum memblock_flags flags)
> + enum memblock_flags flags,
> + bool bottom_up)
> {
> phys_addr_t kernel_end, ret;
>
> @@ -305,9 +307,10 @@ static phys_addr_t __init_memblock memblock_find_in_range_node(phys_addr_t size,
>
> /*
> * try bottom-up allocation only when bottom-up mode
> - * is set and @end is above the kernel image.
> + * is set and @end is above the kernel image or
> + * the bottom-up mode is enforced.
> */
> - if (memblock_bottom_up() && end > kernel_end) {
> + if ((memblock_bottom_up() && end > kernel_end) || bottom_up) {
> phys_addr_t bottom_up_start;
>
> /* make sure we will allocate above the kernel */
> @@ -359,7 +362,7 @@ phys_addr_t __init_memblock memblock_find_in_range(phys_addr_t start,
>
> again:
> ret = memblock_find_in_range_node(size, align, start, end,
> - NUMA_NO_NODE, flags);
> + NUMA_NO_NODE, flags, false);
>
> if (!ret && (flags & MEMBLOCK_MIRROR)) {
> pr_warn("Could not allocate %pap bytes of mirrored memory\n",
> @@ -1331,6 +1334,7 @@ __next_mem_pfn_range_in_zone(u64 *idx, struct zone *zone,
> * @end: the upper bound of the memory region to allocate (phys address)
> * @nid: nid of the free area to find, %NUMA_NO_NODE for any node
> * @exact_nid: control the allocation fall back to other nodes
> + * @bottom_up: force bottom-up allocation
> *
> * The allocation is performed from memory region limited by
> * memblock.current_limit if @end == %MEMBLOCK_ALLOC_ACCESSIBLE.
> @@ -1351,7 +1355,7 @@ __next_mem_pfn_range_in_zone(u64 *idx, struct zone *zone,
> phys_addr_t __init 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)
> + bool exact_nid, bool bottom_up)
> {
> enum memblock_flags flags = choose_memblock_flags();
> phys_addr_t found;
> @@ -1367,14 +1371,14 @@ phys_addr_t __init memblock_alloc_range_nid(phys_addr_t size,
>
> again:
> found = memblock_find_in_range_node(size, align, start, end, nid,
> - flags);
> + flags, bottom_up);
> if (found && !memblock_reserve(found, size))
> goto done;
>
> if (nid != NUMA_NO_NODE && !exact_nid) {
> found = memblock_find_in_range_node(size, align, start,
> end, NUMA_NO_NODE,
> - flags);
> + flags, bottom_up);
> if (found && !memblock_reserve(found, size))
> goto done;
> }
> @@ -1423,7 +1427,7 @@ phys_addr_t __init memblock_phys_alloc_range(phys_addr_t size,
> __func__, (u64)size, (u64)align, &start, &end,
> (void *)_RET_IP_);
> return memblock_alloc_range_nid(size, align, start, end, NUMA_NO_NODE,
> - false);
> + false, false);
> }
>
> /**
> @@ -1442,7 +1446,7 @@ phys_addr_t __init memblock_phys_alloc_range(phys_addr_t size,
> phys_addr_t __init memblock_phys_alloc_try_nid(phys_addr_t size, phys_addr_t align, int nid)
> {
> return memblock_alloc_range_nid(size, align, 0,
> - MEMBLOCK_ALLOC_ACCESSIBLE, nid, false);
> + MEMBLOCK_ALLOC_ACCESSIBLE, nid, false, false);
> }
>
> /**
> @@ -1484,12 +1488,12 @@ static void * __init memblock_alloc_internal(
> max_addr = memblock.current_limit;
>
> alloc = memblock_alloc_range_nid(size, align, min_addr, max_addr, nid,
> - exact_nid);
> + exact_nid, false);
>
> /* retry allocation without lower limit */
> if (!alloc && min_addr)
> alloc = memblock_alloc_range_nid(size, align, 0, max_addr, nid,
> - exact_nid);
> + exact_nid, false);
>
> if (!alloc)
> return NULL;
> --
> 2.26.2
>
--
Sincerely yours,
Mike.
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