| Message ID | 20210702094132.6276-3-ohoono.kwon@samsung.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm: sparse: remove __section_nr() function | expand |
On Fri 02-07-21 18:41:31, 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 > find_memory_block() in order to reduce needless iterations. Yeah, it seems like the only existing user (maybe there used to be more in the past - haven't checked) is just doing pointless translation to comply with the API that doesn't fit it. Just to undo all that work in find_memory_block Nice cleanup and potentially even a performance improvement! > Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com> Acked-by: Michal Hocko <mhocko@suse.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 8377f1f7c78e..905790092e0e 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
On 02.07.21 11:41, 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 > find_memory_block() in order to reduce needless iterations. > > Signed-off-by: Ohhoon Kwon <ohoono.kwon@samsung.com> Reviewed-by: David Hildenbrand <david@redhat.com>
diff --git a/arch/powerpc/platforms/pseries/hotplug-memory.c b/arch/powerpc/platforms/pseries/hotplug-memory.c index 8377f1f7c78e..905790092e0e 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);
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> --- 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(-)