[PATCH v2 5/9] mm: remove CONFIG_DISCONTIGMEM

Mike Rapoport
2021-06-04T06:49:12Z

There are no architectures that support DISCONTIGMEM left.

Remove the configuration option and the dead code it was guarding in the
generic memory management code.

Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
---
include/asm-generic/memory_model.h | 37 ++++--------------------------
include/linux/mmzone.h | 8 ++++---
mm/Kconfig | 25 +++-----------------
mm/page_alloc.c | 13 -----------
4 files changed, 12 insertions(+), 71 deletions(-)

diff --git a/include/asm-generic/memory_model.h b/include/asm-generic/memory_model.h
index 7637fb46ba4f..a2c8ed60233a 100644
--- a/include/asm-generic/memory_model.h
+++ b/include/asm-generic/memory_model.h
@@ -6,47 +6,18 @@

#ifndef __ASSEMBLY__

+/*
+ * supports 3 memory models.
+ */
#if defined(CONFIG_FLATMEM)

#ifndef ARCH_PFN_OFFSET
#define ARCH_PFN_OFFSET (0UL)
#endif

-#elif defined(CONFIG_DISCONTIGMEM)
-
-#ifndef arch_pfn_to_nid
-#define arch_pfn_to_nid(pfn) pfn_to_nid(pfn)
-#endif
-
-#ifndef arch_local_page_offset
-#define arch_local_page_offset(pfn, nid) \
- ((pfn) - NODE_DATA(nid)->node_start_pfn)
-#endif
-
-#endif /* CONFIG_DISCONTIGMEM */
-
-/*
- * supports 3 memory models.
- */
-#if defined(CONFIG_FLATMEM)
-
#define __pfn_to_page(pfn) (mem_map + ((pfn) - ARCH_PFN_OFFSET))
#define __page_to_pfn(page) ((unsigned long)((page) - mem_map) + \
ARCH_PFN_OFFSET)
-#elif defined(CONFIG_DISCONTIGMEM)
-
-#define __pfn_to_page(pfn) \
-({ unsigned long __pfn = (pfn); \
- unsigned long __nid = arch_pfn_to_nid(__pfn); \
- NODE_DATA(__nid)->node_mem_map + arch_local_page_offset(__pfn, __nid);\
-})
-
-#define __page_to_pfn(pg) \
-({ const struct page *__pg = (pg); \
- struct pglist_data *__pgdat = NODE_DATA(page_to_nid(__pg)); \
- (unsigned long)(__pg - __pgdat->node_mem_map) + \
- __pgdat->node_start_pfn; \
-})

#elif defined(CONFIG_SPARSEMEM_VMEMMAP)

@@ -70,7 +41,7 @@
struct mem_section *__sec = __pfn_to_section(__pfn); \
__section_mem_map_addr(__sec) + __pfn; \
})
-#endif /* CONFIG_FLATMEM/DISCONTIGMEM/SPARSEMEM */
+#endif /* CONFIG_FLATMEM/SPARSEMEM */

/*
* Convert a physical address to a Page Frame Number and back
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 0d53eba1c383..700032e99419 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -738,10 +738,12 @@ struct zonelist {
struct zoneref _zonerefs[MAX_ZONES_PER_ZONELIST + 1];
};

-#ifndef CONFIG_DISCONTIGMEM
-/* The array of struct pages - for discontigmem use pgdat->lmem_map */
+/*
+ * The array of struct pages for flatmem.
+ * It must be declared for SPARSEMEM as well because there are configurations
+ * that rely on that.
+ */
extern struct page *mem_map;
-#endif

#ifdef CONFIG_TRANSPARENT_HUGEPAGE
struct deferred_split {
diff --git a/mm/Kconfig b/mm/Kconfig
index 02d44e3420f5..218b96ccc84a 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -19,7 +19,7 @@ choice

config FLATMEM_MANUAL
bool "Flat Memory"
- depends on !(ARCH_DISCONTIGMEM_ENABLE || ARCH_SPARSEMEM_ENABLE) || ARCH_FLATMEM_ENABLE
+ depends on !ARCH_SPARSEMEM_ENABLE || ARCH_FLATMEM_ENABLE
help
This option is best suited for non-NUMA systems with
flat address space. The FLATMEM is the most efficient
@@ -32,21 +32,6 @@ config FLATMEM_MANUAL

If unsure, choose this option (Flat Memory) over any other.

-config DISCONTIGMEM_MANUAL
- bool "Discontiguous Memory"
- depends on ARCH_DISCONTIGMEM_ENABLE
- help
- This option provides enhanced support for discontiguous
- memory systems, over FLATMEM. These systems have holes
- in their physical address spaces, and this option provides
- more efficient handling of these holes.
-
- Although "Discontiguous Memory" is still used by several
- architectures, it is considered deprecated in favor of
- "Sparse Memory".
-
- If unsure, choose "Sparse Memory" over this option.
-
config SPARSEMEM_MANUAL
bool "Sparse Memory"
depends on ARCH_SPARSEMEM_ENABLE
@@ -62,17 +47,13 @@ config SPARSEMEM_MANUAL

endchoice

-config DISCONTIGMEM
- def_bool y
- depends on (!SELECT_MEMORY_MODEL && ARCH_DISCONTIGMEM_ENABLE) || DISCONTIGMEM_MANUAL
-
config SPARSEMEM
def_bool y
depends on (!SELECT_MEMORY_MODEL && ARCH_SPARSEMEM_ENABLE) || SPARSEMEM_MANUAL

config FLATMEM
def_bool y
- depends on (!DISCONTIGMEM && !SPARSEMEM) || FLATMEM_MANUAL
+ depends on !SPARSEMEM || FLATMEM_MANUAL

config FLAT_NODE_MEM_MAP
def_bool y
@@ -85,7 +66,7 @@ config FLAT_NODE_MEM_MAP
#
config NEED_MULTIPLE_NODES
def_bool y
- depends on DISCONTIGMEM || NUMA
+ depends on NUMA

#
# SPARSEMEM_EXTREME (which is the default) does some bootmem
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index aaa1655cf682..6fc22482eaa8 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -331,20 +331,7 @@ compound_page_dtor * const compound_page_dtors[NR_COMPOUND_DTORS] = {

int min_free_kbytes = 1024;
int user_min_free_kbytes = -1;
-#ifdef CONFIG_DISCONTIGMEM
-/*
- * DiscontigMem defines memory ranges as separate pg_data_t even if the ranges
- * are not on separate NUMA nodes. Functionally this works but with
- * watermark_boost_factor, it can reclaim prematurely as the ranges can be
- * quite small. By default, do not boost watermarks on discontigmem as in
- * many cases very high-order allocations like THP are likely to be
- * unsupported and the premature reclaim offsets the advantage of long-term
- * fragmentation avoidance.
- */
-int watermark_boost_factor __read_mostly;
-#else
int watermark_boost_factor __read_mostly = 15000;
-#endif
int watermark_scale_factor = 10;

static unsigned long nr_kernel_pages __initdata;
--
2.28.0