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Subject[PATCH] mm: cma: allocate cma areas bottom-up
Date
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 <guro@fb.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
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