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From: Ohhoon Kwon <ohoono.kwon@samsung.com>
To: david@redhat.com, ohoono.kwon@samsung.com,
	akpm@linux-foundation.org, mhocko@suse.com
Cc: bhe@redhat.com, rppt@linux.ibm.com, ohkwon1043@gmail.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: [PATCH v2 2/3] mm: sparse: pass section_nr to find_memory_block
Date: Mon,  5 Jul 2021 17:55:37 +0900	[thread overview]
Message-ID: <20210705085538.14557-3-ohoono.kwon@samsung.com> (raw)
In-Reply-To: <20210705085538.14557-1-ohoono.kwon@samsung.com>

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


  parent reply	other threads:[~2021-07-05  8:59 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20210705085918epcas1p1493a3b289b3144bf86e90893185c088a@epcas1p1.samsung.com>
2021-07-05  8:55 ` [PATCH v2 0/3] mm: sparse: remove __section_nr() function Ohhoon Kwon
     [not found]   ` <CGME20210705085918epcas1p17e0ac84d91c591897d00fbc3d3caa771@epcas1p1.samsung.com>
2021-07-05  8:55     ` [PATCH v2 1/3] mm: sparse: pass section_nr to section_mark_present Ohhoon Kwon
2021-07-07  9:12       ` Michal Hocko
     [not found]   ` <CGME20210705085918epcas1p3fdaf2bc0de2f1017c3057aeb6e8c82a7@epcas1p3.samsung.com>
2021-07-05  8:55     ` Ohhoon Kwon [this message]
     [not found]   ` <CGME20210705085918epcas1p415e226a85dc289c2d306c009dbc4ef55@epcas1p4.samsung.com>
2021-07-05  8:55     ` [PATCH v2 3/3] mm: sparse: remove __section_nr() function Ohhoon Kwon

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