mm: sparse: pass section_nr to find_memory_block

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.

Link: https://lkml.kernel.org/r/20210707150212.855-3-ohoono.kwon@samsung.com
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>
Cc: Baoquan He <bhe@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c
index 377d852..d4f28ee 100644 (file)
--- 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 aa31a21..e3fd2db 100644 (file)
--- 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 97e92e8..d9a0b61 100644 (file)
--- 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);