[PATCH v2 0/3] mm: sparse: remove __section_nr() function

[PATCH v2 0/3] mm: sparse: remove __section_nr() function

[Ohhoon Kwon]

This series contains cleanups to remove __section_nr().

There were no code changes but only some modifications on commit
messages compared to the initial PATCH mailing list.

Also, I appended acked-by's and reviewed-by's from the initial mailing
list for convenience.

Ohhoon Kwon (3):
  mm: sparse: pass section_nr to section_mark_present
  mm: sparse: pass section_nr to find_memory_block
  mm: sparse: remove __section_nr() function

 .../platforms/pseries/hotplug-memory.c        |  4 +--
 drivers/base/memory.c                         |  4 +--
 include/linux/memory.h                        |  2 +-
 include/linux/mmzone.h                        |  1 -
 mm/sparse.c                                   | 35 +++----------------
 5 files changed, 9 insertions(+), 37 deletions(-)

-- 
2.17.1

[PATCH v2 1/3] mm: sparse: pass section_nr to section_mark_present

[Ohhoon Kwon]

With CONFIG_SPARSEMEM_EXTREME enabled, __section_nr() which converts
mem_section to section_nr could be costly since it iterates all
section roots to check if the given mem_section is in its range.

On the other hand, __nr_to_section() which converts section_nr to
mem_section can be done in O(1).

Let's pass section_nr instead of mem_section ptr to
section_mark_present() in order to reduce needless iterations.

Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 mm/sparse.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/mm/sparse.c b/mm/sparse.c
index 6326cdf36c4f..b4fae2fc6276 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -187,13 +187,14 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
  * those loops early.
  */
 unsigned long __highest_present_section_nr;
-static void section_mark_present(struct mem_section *ms)
+static void section_mark_present(unsigned long section_nr)
 {
-	unsigned long section_nr = __section_nr(ms);
+	struct mem_section *ms;
 
 	if (section_nr > __highest_present_section_nr)
 		__highest_present_section_nr = section_nr;
 
+	ms = __nr_to_section(section_nr);
 	ms->section_mem_map |= SECTION_MARKED_PRESENT;
 }
 
@@ -280,7 +281,7 @@ static void __init memory_present(int nid, unsigned long start, unsigned long en
 		if (!ms->section_mem_map) {
 			ms->section_mem_map = sparse_encode_early_nid(nid) |
 							SECTION_IS_ONLINE;
-			section_mark_present(ms);
+			section_mark_present(section);
 		}
 	}
 }
@@ -934,7 +935,7 @@ int __meminit sparse_add_section(int nid, unsigned long start_pfn,
 
 	ms = __nr_to_section(section_nr);
 	set_section_nid(section_nr, nid);
-	section_mark_present(ms);
+	section_mark_present(section_nr);
 
 	/* Align memmap to section boundary in the subsection case */
 	if (section_nr_to_pfn(section_nr) != start_pfn)
-- 
2.17.1

[PATCH v2 2/3] mm: sparse: pass section_nr to find_memory_block

[Ohhoon Kwon]

With CONFIG_SPARSEMEM_EXTREME enabled, __section_nr() which converts
mem_section to section_nr could be costly since it iterates all
section roots to check if the given mem_section is in its range.

On the other hand, __nr_to_section() which converts section_nr to
mem_section can be done in O(1).

Let's pass section_nr instead of mem_section ptr to
find_memory_block() in order to reduce needless iterations.

Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 arch/powerpc/platforms/pseries/hotplug-memory.c | 4 +---
 drivers/base/memory.c                           | 4 ++--
 include/linux/memory.h                          | 2 +-
 3 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 377d852f5a9a..d4f28ee4d5dc 100644
--- a/arch/powerpc/platforms/pseries/hotplug-memory.c
+++ b/arch/powerpc/platforms/pseries/hotplug-memory.c
@@ -211,13 +211,11 @@ static int update_lmb_associativity_index(struct drmem_lmb *lmb)
 static struct memory_block *lmb_to_memblock(struct drmem_lmb *lmb)
 {
 	unsigned long section_nr;
-	struct mem_section *mem_sect;
 	struct memory_block *mem_block;
 
 	section_nr = pfn_to_section_nr(PFN_DOWN(lmb->base_addr));
-	mem_sect = __nr_to_section(section_nr);
 
-	mem_block = find_memory_block(mem_sect);
+	mem_block = find_memory_block(section_nr);
 	return mem_block;
 }
 
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index d5ffaab3cb61..e31598955cc4 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -578,9 +578,9 @@ static struct memory_block *find_memory_block_by_id(unsigned long block_id)
 /*
  * Called under device_hotplug_lock.
  */
-struct memory_block *find_memory_block(struct mem_section *section)
+struct memory_block *find_memory_block(unsigned long section_nr)
 {
-	unsigned long block_id = memory_block_id(__section_nr(section));
+	unsigned long block_id = memory_block_id(section_nr);
 
 	return find_memory_block_by_id(block_id);
 }
diff --git a/include/linux/memory.h b/include/linux/memory.h
index 97e92e8b556a..d9a0b61cd432 100644
--- a/include/linux/memory.h
+++ b/include/linux/memory.h
@@ -90,7 +90,7 @@ int create_memory_block_devices(unsigned long start, unsigned long size,
 void remove_memory_block_devices(unsigned long start, unsigned long size);
 extern void memory_dev_init(void);
 extern int memory_notify(unsigned long val, void *v);
-extern struct memory_block *find_memory_block(struct mem_section *);
+extern struct memory_block *find_memory_block(unsigned long section_nr);
 typedef int (*walk_memory_blocks_func_t)(struct memory_block *, void *);
 extern int walk_memory_blocks(unsigned long start, unsigned long size,
 			      void *arg, walk_memory_blocks_func_t func);
-- 
2.17.1

[PATCH v2 3/3] mm: sparse: remove __section_nr() function

[Ohhoon Kwon]

As the last users of __section_nr() are gone, let's remove unused
function __section_nr().

Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Mike Rapoport <rppt@linux.ibm.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
---
 include/linux/mmzone.h |  1 -
 mm/sparse.c            | 26 --------------------------
 2 files changed, 27 deletions(-)

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index fcb535560028..8827f4d081d4 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -1342,7 +1342,6 @@ static inline struct mem_section *__nr_to_section(unsigned long nr)
 		return NULL;
 	return &mem_section[SECTION_NR_TO_ROOT(nr)][nr & SECTION_ROOT_MASK];
 }
-extern unsigned long __section_nr(struct mem_section *ms);
 extern size_t mem_section_usage_size(void);
 
 /*
diff --git a/mm/sparse.c b/mm/sparse.c
index b4fae2fc6276..c14d2b37fd16 100644
--- a/mm/sparse.c
+++ b/mm/sparse.c
@@ -109,32 +109,6 @@ static inline int sparse_index_init(unsigned long section_nr, int nid)
 }
 #endif
 
-#ifdef CONFIG_SPARSEMEM_EXTREME
-unsigned long __section_nr(struct mem_section *ms)
-{
-	unsigned long root_nr;
-	struct mem_section *root = NULL;
-
-	for (root_nr = 0; root_nr < NR_SECTION_ROOTS; root_nr++) {
-		root = __nr_to_section(root_nr * SECTIONS_PER_ROOT);
-		if (!root)
-			continue;
-
-		if ((ms >= root) && (ms < (root + SECTIONS_PER_ROOT)))
-		     break;
-	}
-
-	VM_BUG_ON(!root);
-
-	return (root_nr * SECTIONS_PER_ROOT) + (ms - root);
-}
-#else
-unsigned long __section_nr(struct mem_section *ms)
-{
-	return (unsigned long)(ms - mem_section[0]);
-}
-#endif
-
 /*
  * During early boot, before section_mem_map is used for an actual
  * mem_map, we use section_mem_map to store the section's NUMA
-- 
2.17.1

Re: [PATCH v2 1/3] mm: sparse: pass section_nr to section_mark_present

[Michal Hocko]

On Mon 05-07-21 17:55:36, Ohhoon Kwon wrote:
> With CONFIG_SPARSEMEM_EXTREME enabled, __section_nr() which converts
> mem_section to section_nr could be costly since it iterates all
> section roots to check if the given mem_section is in its range.
> 
> On the other hand, __nr_to_section() which converts section_nr to
> mem_section can be done in O(1).
> 
> Let's pass section_nr instead of mem_section ptr to
> section_mark_present() in order to reduce needless iterations.
> 
> Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com>
> Acked-by: Michal Hocko <mhocko@suse.com>
> Acked-by: Mike Rapoport <rppt@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
>  mm/sparse.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/sparse.c b/mm/sparse.c
> index 6326cdf36c4f..b4fae2fc6276 100644
> --- a/mm/sparse.c
> +++ b/mm/sparse.c
> @@ -187,13 +187,14 @@ void __meminit mminit_validate_memmodel_limits(unsigned long *start_pfn,
>   * those loops early.
>   */
>  unsigned long __highest_present_section_nr;
> -static void section_mark_present(struct mem_section *ms)
> +static void section_mark_present(unsigned long section_nr)
>  {
> -	unsigned long section_nr = __section_nr(ms);
> +	struct mem_section *ms;
>  
>  	if (section_nr > __highest_present_section_nr)
>  		__highest_present_section_nr = section_nr;
>  
> +	ms = __nr_to_section(section_nr);
>  	ms->section_mem_map |= SECTION_MARKED_PRESENT;

Can you add the ms parameter here so that we get rid of the pointless
__nr_to_section as suggested in the previous review feedback?
-- 
Michal Hocko
SUSE Labs