diff mbox series

[v3,4/7] mm/sparse.c: only use subsection map in VMEMMAP case

Message ID 20200307084229.28251-5-bhe@redhat.com (mailing list archive)
State New, archived
Headers show
Series mm/hotplug: Only use subsection map for VMEMMAP | expand

Commit Message

Baoquan He March 7, 2020, 8:42 a.m. UTC 
Currently, to support subsection aligned memory region adding for pmem,
subsection map is added to track which subsection is present.

However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means
subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the
classic sparse, subsection map is meaningless and confusing.

About the classic sparse which doesn't support subsection hotplug, Dan
said it's more because the effort and maintenance burden outweighs the
benefit. Besides, the current 64 bit ARCHes all enable
SPARSEMEM_VMEMMAP_ENABLE by default.

Combining the above reasons, no need to provide subsection map and the
relevant handling for the classic sparse. Handle it with this patch.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 include/linux/mmzone.h |  2 ++
 mm/sparse.c            | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

Comments

David Hildenbrand March 9, 2020, 9 a.m. UTC | #1 
On 07.03.20 09:42, Baoquan He wrote:
> Currently, to support subsection aligned memory region adding for pmem,
> subsection map is added to track which subsection is present.
> 
> However, config ZONE_DEVICE depends on SPARSEMEM_VMEMMAP. It means
> subsection map only makes sense when SPARSEMEM_VMEMMAP enabled. For the
> classic sparse, subsection map is meaningless and confusing.
> 
> About the classic sparse which doesn't support subsection hotplug, Dan
> said it's more because the effort and maintenance burden outweighs the
> benefit. Besides, the current 64 bit ARCHes all enable
> SPARSEMEM_VMEMMAP_ENABLE by default.
> 
> Combining the above reasons, no need to provide subsection map and the
> relevant handling for the classic sparse. Handle it with this patch.
> 
> Signed-off-by: Baoquan He <bhe@redhat.com>
> ---
>  include/linux/mmzone.h |  2 ++
>  mm/sparse.c            | 25 +++++++++++++++++++++++++
>  2 files changed, 27 insertions(+)
> 
> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> index 42b77d3b68e8..f3f264826423 100644
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1143,7 +1143,9 @@ static inline unsigned long section_nr_to_pfn(unsigned long sec)
>  #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
>  
>  struct mem_section_usage {
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
>  	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
> +#endif
>  	/* See declaration of similar field in struct zone */
>  	unsigned long pageblock_flags[0];
>  };
> diff --git a/mm/sparse.c b/mm/sparse.c
> index d9dcd58d5c1d..2142045ab5c5 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -209,6 +209,7 @@ static inline unsigned long first_present_section_nr(void)
>  	return next_present_section_nr(-1);
>  }
>  
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
>  static void subsection_mask_set(unsigned long *map, unsigned long pfn,
>  		unsigned long nr_pages)
>  {
> @@ -243,6 +244,11 @@ void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
>  		nr_pages -= pfns;
>  	}
>  }
> +#else
> +void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
> +{
> +}
> +#endif
>  
>  /* Record a memory area against a node. */
>  void __init memory_present(int nid, unsigned long start, unsigned long end)
> @@ -726,6 +732,7 @@ static void free_map_bootmem(struct page *memmap)
>  }
>  #endif /* CONFIG_SPARSEMEM_VMEMMAP */
>  
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
>  static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
>  {
>  	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
> @@ -753,6 +760,17 @@ static bool is_subsection_map_empty(struct mem_section *ms)
>  	return bitmap_empty(&ms->usage->subsection_map[0],
>  			    SUBSECTIONS_PER_SECTION);
>  }
> +#else
> +static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
> +{
> +	return 0;
> +}
> +
> +static bool is_subsection_map_empty(struct mem_section *ms)
> +{
> +	return true;
> +}
> +#endif
>  
>  static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>  		struct vmem_altmap *altmap)
> @@ -809,6 +827,7 @@ static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
>  		ms->section_mem_map = (unsigned long)NULL;
>  }
>  
> +#ifdef CONFIG_SPARSEMEM_VMEMMAP
>  static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>  {
>  	struct mem_section *ms = __pfn_to_section(pfn);
> @@ -830,6 +849,12 @@ static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
>  
>  	return rc;
>  }
> +#else
> +static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
> +{
> +	return 0;
> +}
> +#endif
>  
>  static struct page * __meminit section_activate(int nid, unsigned long pfn,
>  		unsigned long nr_pages, struct vmem_altmap *altmap)
> 

Reviewed-by: David Hildenbrand <david@redhat.com>
diff mbox series

Patch

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 42b77d3b68e8..f3f264826423 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1143,7 +1143,9 @@  static inline unsigned long section_nr_to_pfn(unsigned long sec)
 #define SUBSECTION_ALIGN_DOWN(pfn) ((pfn) & PAGE_SUBSECTION_MASK)
 
 struct mem_section_usage {
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 	DECLARE_BITMAP(subsection_map, SUBSECTIONS_PER_SECTION);
+#endif
 	/* See declaration of similar field in struct zone */
 	unsigned long pageblock_flags[0];
 };
diff --git a/mm/sparse.c b/mm/sparse.c
index d9dcd58d5c1d..2142045ab5c5 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -209,6 +209,7 @@  static inline unsigned long first_present_section_nr(void)
 	return next_present_section_nr(-1);
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static void subsection_mask_set(unsigned long *map, unsigned long pfn,
 		unsigned long nr_pages)
 {
@@ -243,6 +244,11 @@  void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
 		nr_pages -= pfns;
 	}
 }
+#else
+void __init subsection_map_init(unsigned long pfn, unsigned long nr_pages)
+{
+}
+#endif
 
 /* Record a memory area against a node. */
 void __init memory_present(int nid, unsigned long start, unsigned long end)
@@ -726,6 +732,7 @@  static void free_map_bootmem(struct page *memmap)
 }
 #endif /* CONFIG_SPARSEMEM_VMEMMAP */
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	DECLARE_BITMAP(map, SUBSECTIONS_PER_SECTION) = { 0 };
@@ -753,6 +760,17 @@  static bool is_subsection_map_empty(struct mem_section *ms)
 	return bitmap_empty(&ms->usage->subsection_map[0],
 			    SUBSECTIONS_PER_SECTION);
 }
+#else
+static int clear_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+
+static bool is_subsection_map_empty(struct mem_section *ms)
+{
+	return true;
+}
+#endif
 
 static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		struct vmem_altmap *altmap)
@@ -809,6 +827,7 @@  static void section_deactivate(unsigned long pfn, unsigned long nr_pages,
 		ms->section_mem_map = (unsigned long)NULL;
 }
 
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
 static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 {
 	struct mem_section *ms = __pfn_to_section(pfn);
@@ -830,6 +849,12 @@  static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
 
 	return rc;
 }
+#else
+static int fill_subsection_map(unsigned long pfn, unsigned long nr_pages)
+{
+	return 0;
+}
+#endif
 
 static struct page * __meminit section_activate(int nid, unsigned long pfn,
 		unsigned long nr_pages, struct vmem_altmap *altmap)