Re: [RFC PATCH v3 1/3] mm: Factor out the pagetable pages account into new helper function

Baolin Wang
2022-07-01T08:01:11Z

On 6/30/2022 10:11 PM, Mike Rapoport wrote:
> On Thu, Jun 30, 2022 at 07:11:14PM +0800, Baolin Wang wrote:
>> Factor out the pagetable pages account into new helper functions to avoid
>> duplicated code. Meanwhile these helper functions also will be used to
>> account pagetable pages which do not need split pagetale lock.
>>
>> Meanwhile convert to use mod_lruvec_page_state() in case of non-order-0
>> page table allocation.
>
> These are *very* rare. I think only parisc may have non-order-0 pmd and pud
> tables.

s390 also has non-order-0 page table allocation, but they both do not
use the generic page table allocation now.

> With that, I'd suggest making use of compound_nr() build time opt-in.

After more thinking, I'd prefer to change back to use
inc_lruvec_page_state()/dec_lruvec_page_state(), since now no
architecures will need non-order-0 page table allocation.

After this patchset, I plan to convert parisc and s390 to use generic
pagetable allocation, then I will add non-order-0 page table allocation
support. Like Matthew suggested, maybe I need change the API to pass the
number of pages.

>> Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
>> ---
>> include/linux/mm.h | 24 ++++++++++++++++--------
>> 1 file changed, 16 insertions(+), 8 deletions(-)
>>
>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>> index a2270e3..3be6d2c 100644
>> --- a/include/linux/mm.h
>> +++ b/include/linux/mm.h
>> @@ -2353,20 +2353,30 @@ static inline void pgtable_init(void)
>> pgtable_cache_init();
>> }
>>
>> +static inline void pgtable_page_inc(struct page *page)
>> +{
>> + __SetPageTable(page);
>> + mod_lruvec_page_state(page, NR_PAGETABLE, compound_nr(page));
>> +}
>> +
>> +static inline void pgtable_page_dec(struct page *page)
>> +{
>> + __ClearPageTable(page);
>> + mod_lruvec_page_state(page, NR_PAGETABLE, -compound_nr(page));
>> +}
>> +
>> static inline bool pgtable_pte_page_ctor(struct page *page)
>> {
>> if (!ptlock_init(page))
>> return false;
>> - __SetPageTable(page);
>> - inc_lruvec_page_state(page, NR_PAGETABLE);
>> + pgtable_page_inc(page);
>> return true;
>> }
>>
>> static inline void pgtable_pte_page_dtor(struct page *page)
>> {
>> ptlock_free(page);
>> - __ClearPageTable(page);
>> - dec_lruvec_page_state(page, NR_PAGETABLE);
>> + pgtable_page_dec(page);
>> }
>>
>> #define pte_offset_map_lock(mm, pmd, address, ptlp) \
>> @@ -2452,16 +2462,14 @@ static inline bool pgtable_pmd_page_ctor(struct page *page)
>> {
>> if (!pmd_ptlock_init(page))
>> return false;
>> - __SetPageTable(page);
>> - inc_lruvec_page_state(page, NR_PAGETABLE);
>> + pgtable_page_inc(page);
>> return true;
>> }
>>
>> static inline void pgtable_pmd_page_dtor(struct page *page)
>> {
>> pmd_ptlock_free(page);
>> - __ClearPageTable(page);
>> - dec_lruvec_page_state(page, NR_PAGETABLE);
>> + pgtable_page_dec(page);
>> }
>>
>> /*
>> --
>> 1.8.3.1
>>
>