On Sun, Jul 07, 2024 at 10:17:27AM +0200, David Hildenbrand wrote:
>On 06.07.24 03:28, Wei Yang wrote:
>> On Fri, Jul 05, 2024 at 12:09:48PM +0300, Mike Rapoport wrote:
>> > On Wed, Jul 03, 2024 at 12:51:49AM +0000, Wei Yang wrote:
>> > > Instead of using raw memblock api, we wrap a new helper for user.
>> >
>> > The changelog should be more elaborate and explain why this function is
>> > needed.
>> >
>> > > Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>> > > ---
>> > > include/linux/memblock.h | 1 +
>> > > mm/memblock.c | 19 +++++++++++++++++++
>> > > 2 files changed, 20 insertions(+)
>> > >
>> > > diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>> > > index 40c62aca36ec..7d1c32b3dc12 100644
>> > > --- a/include/linux/memblock.h
>> > > +++ b/include/linux/memblock.h
>> > > @@ -486,6 +486,7 @@ static inline __init_memblock bool memblock_bottom_up(void)
>> > > phys_addr_t memblock_phys_mem_size(void);
>> > > phys_addr_t memblock_reserved_size(void);
>> > > +unsigned long memblock_estimated_nr_pages(void);
>> > > phys_addr_t memblock_start_of_DRAM(void);
>> > > phys_addr_t memblock_end_of_DRAM(void);
>> > > void memblock_enforce_memory_limit(phys_addr_t memory_limit);
>> > > diff --git a/mm/memblock.c b/mm/memblock.c
>> > > index e81fb68f7f88..c1f1aac0459f 100644
>> > > --- a/mm/memblock.c
>> > > +++ b/mm/memblock.c
>> > > @@ -1729,6 +1729,25 @@ phys_addr_t __init_memblock memblock_reserved_size(void)
>> > > return memblock.reserved.total_size;
>> > > }
>> > > +/**
>> > > + * memblock_estimated_nr_pages - return number of pages from memblock point of
>> > > + * view
>> >
>> > This function returns the estimate for free pages, not the number of pages
>> > in RAM.
>> >
>> > How about memblock_estimated_nr_free_pages()?
>> >
>> > > + * some calculation before all pages are freed to buddy system, especially
>> > > + * when CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
>> >
>> > I'm failing to parse this sentence. The return value here won't depend on
>> > CONFIG_DEFERRED_STRUCT_PAGE_INIT.
>> >
>> > > + *
>> > > + * At this point, we can get this information from memblock. Since the system
>> > > + * state is not settle down and address alignment, the value is an estimation.
>> > > + *
>> > > + * Return:
>> > > + * An estimated number of pages from memblock point of view.
>> >
>> > ^ free
>> >
>> > > + */
>> > > +unsigned long __init memblock_estimated_nr_pages(void)
>> > > +{
>> > > + return PHYS_PFN(memblock_phys_mem_size() - memblock_reserved_size());
>> > > +}
>> > > +
>> > > /* lowest address */
>> > > phys_addr_t __init_memblock memblock_start_of_DRAM(void)
>> > > {
>> > > --
>> > > 2.34.1
>> > >
>>
>> Thanks for review. Is this one looks better?
>>
>> Subject: [PATCH] mm/memblock: introduce a new helper memblock_estimated_nr_free_pages()
>>
>> During bootup, system may need the number of free pages in the whole system
>> to do some calculation before all pages are freed to buddy system. Usually
>> this number is get from totalram_pages(). Since we plan to move the free
>> pages accounting in __free_pages_core(), this value may not represent
>> total free pages at the early stage, especially when
>> CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
>>
>> Instead of using raw memblock api, let's introduce a new helper for user
>> to get the estimated number of free pages from memblock point of view.
>>
>> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxx>
>> CC: David Hildenbrand <david@xxxxxxxxxx>
>> ---
>> include/linux/memblock.h | 1 +
>> mm/memblock.c | 22 ++++++++++++++++++++++
>> 2 files changed, 23 insertions(+)
>>
>> diff --git a/include/linux/memblock.h b/include/linux/memblock.h
>> index 40c62aca36ec..7d1c32b3dc12 100644
>> --- a/include/linux/memblock.h
>> +++ b/include/linux/memblock.h
>> @@ -486,6 +486,7 @@ static inline __init_memblock bool memblock_bottom_up(void)
>> phys_addr_t memblock_phys_mem_size(void);
>> phys_addr_t memblock_reserved_size(void);
>> +unsigned long memblock_estimated_nr_pages(void);
>> phys_addr_t memblock_start_of_DRAM(void);
>> phys_addr_t memblock_end_of_DRAM(void);
>> void memblock_enforce_memory_limit(phys_addr_t memory_limit);
>> diff --git a/mm/memblock.c b/mm/memblock.c
>> index e81fb68f7f88..00decc42e02b 100644
>> --- a/mm/memblock.c
>> +++ b/mm/memblock.c
>> @@ -1729,6 +1729,28 @@ phys_addr_t __init_memblock memblock_reserved_size(void)
>> return memblock.reserved.total_size;
>> }
>> +/**
>> + * memblock_estimated_nr_free_pages - return estimated number of free pages
>> + * from memblock point of view
>> + *
>> + * During bootup, system may need the number of free pages in the whole system
>> + * to do some calculation before all pages are freed to buddy system. Usually
>> + * this number is get from totalram_pages(). Since we plan to move the free
>> + * pages accounting in __free_pages_core(), this value may not represent total
>> + * free pages at the early stage, especially when > + * CONFIG_DEFERRED_STRUCT_PAGE_INIT is enabled.
>
>These historical details should be dropped. "Since we plan ..." will easily
>get outdated soon.
>
>* During bootup, subsystems might need a rough estimate of the number of *
>free pages in the whole system, before precise numbers are available
>* from the buddy. Especially with CONFIG_DEFERRED_STRUCT_PAGE_INIT, the
>* numbers obtained from the buddy might be very imprecise during bootup.
>
Pretty better, thanks :-)
>?
>
>Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
>
>--
>Cheers,
>
>David / dhildenb
--
Wei Yang
Help you, Help me
