| Message ID | 20230616110826.344417-9-aneesh.kumar@linux.ibm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for DAX vmemmap optimization for ppc64 | expand |
On 16/06/2023 12:08, Aneesh Kumar K.V wrote: > dax vmemmap optimization requires a minimum of 2 PAGE_SIZE area within > vmemmap such that tail page mapping can point to the second PAGE_SIZE area. > Enforce that in vmemmap_can_optimize() function. > > Architectures like powerpc also want to enable vmemmap optimization > conditionally (only with radix MMU translation). Hence allow architecture > override. > This makes sense. The enforcing here is not just for correctness but because you want to use VMEMMAP_RESERVE_NR supposedly? I would suggest having two patches one for the refactor and another one for the override, but I don't feel particularly strongly about it. > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > --- > include/linux/mm.h | 30 ++++++++++++++++++++++++++---- > mm/mm_init.c | 2 +- > 2 files changed, 27 insertions(+), 5 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 27ce77080c79..9a45e61cd83f 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -31,6 +31,8 @@ > #include <linux/memremap.h> > #include <linux/slab.h> > > +#include <asm/page.h> > + Why is this include needed? > struct mempolicy; > struct anon_vma; > struct anon_vma_chain; > @@ -3550,13 +3552,33 @@ void vmemmap_free(unsigned long start, unsigned long end, > struct vmem_altmap *altmap); > #endif > > +#define VMEMMAP_RESERVE_NR 2 see below > #ifdef CONFIG_ARCH_WANT_OPTIMIZE_VMEMMAP > -static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, > - struct dev_pagemap *pgmap) > +static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap, > + struct dev_pagemap *pgmap) > { > - return is_power_of_2(sizeof(struct page)) && > - pgmap && (pgmap_vmemmap_nr(pgmap) > 1) && !altmap; > + if (pgmap) { > + unsigned long nr_pages; > + unsigned long nr_vmemmap_pages; > + > + nr_pages = pgmap_vmemmap_nr(pgmap); > + nr_vmemmap_pages = ((nr_pages * sizeof(struct page)) >> PAGE_SHIFT); > + /* > + * For vmemmap optimization with DAX we need minimum 2 vmemmap > + * pages. See layout diagram in Documentation/mm/vmemmap_dedup.rst > + */ > + return is_power_of_2(sizeof(struct page)) && > + (nr_vmemmap_pages > VMEMMAP_RESERVE_NR) && !altmap; > + } It would be more readable (i.e. less identation) if you just reverse this: unsigned long nr_vmemmap_pages; if (!pgmap || !is_power_of_2(sizeof(struct page)) return false; nr_vmemmap_pages = ((pgmap_vmemmap_nr(pgmap) * sizeof(struct page)) >> PAGE_SHIFT); /* * For vmemmap optimization with DAX we need minimum 2 vmemmap * pages. See layout diagram in Documentation/mm/vmemmap_dedup.rst */ return (nr_vmemmap_pages > VMEMMAP_RESERVE_NR) && !altmap; > + return false; > } > +/* > + * If we don't have an architecture override, use the generic rule > + */ > +#ifndef vmemmap_can_optimize > +#define vmemmap_can_optimize __vmemmap_can_optimize > +#endif > + sparse-vmemmap code is trivial to change to use dedup a single vmemmap page (e.g. to align with hugetlb), hopefully the architecture override to do. this is to say whether VMEMMAP_RESERVE_NR should have similar to above? > #else > static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, > struct dev_pagemap *pgmap) > diff --git a/mm/mm_init.c b/mm/mm_init.c > index 7f7f9c677854..d1676afc94f1 100644 > --- a/mm/mm_init.c > +++ b/mm/mm_init.c > @@ -1020,7 +1020,7 @@ static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, > if (!vmemmap_can_optimize(altmap, pgmap)) > return pgmap_vmemmap_nr(pgmap); > > - return 2 * (PAGE_SIZE / sizeof(struct page)); > + return VMEMMAP_RESERVE_NR * (PAGE_SIZE / sizeof(struct page)); > } > > static void __ref memmap_init_compound(struct page *head,
Joao Martins <joao.m.martins@oracle.com> writes: > On 16/06/2023 12:08, Aneesh Kumar K.V wrote: >> dax vmemmap optimization requires a minimum of 2 PAGE_SIZE area within >> vmemmap such that tail page mapping can point to the second PAGE_SIZE area. >> Enforce that in vmemmap_can_optimize() function. >> >> Architectures like powerpc also want to enable vmemmap optimization >> conditionally (only with radix MMU translation). Hence allow architecture >> override. >> > This makes sense. The enforcing here is not just for correctness but because you > want to use VMEMMAP_RESERVE_NR supposedly? > > I would suggest having two patches one for the refactor and another one for the > override, but I don't feel particularly strongly about it. > I will wait for feedback from others. If we have others also suggesting for the split patch I will do that. >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >> --- >> include/linux/mm.h | 30 ++++++++++++++++++++++++++---- >> mm/mm_init.c | 2 +- >> 2 files changed, 27 insertions(+), 5 deletions(-) >> >> diff --git a/include/linux/mm.h b/include/linux/mm.h >> index 27ce77080c79..9a45e61cd83f 100644 >> --- a/include/linux/mm.h >> +++ b/include/linux/mm.h >> @@ -31,6 +31,8 @@ >> #include <linux/memremap.h> >> #include <linux/slab.h> >> >> +#include <asm/page.h> >> + > > Why is this include needed? That was for PAGE_SHIFT. But then we do pull that through other include dependencies. I will see if i can drop that. > >> struct mempolicy; >> struct anon_vma; >> struct anon_vma_chain; >> @@ -3550,13 +3552,33 @@ void vmemmap_free(unsigned long start, unsigned long end, >> struct vmem_altmap *altmap); >> #endif >> >> +#define VMEMMAP_RESERVE_NR 2 > > see below > >> #ifdef CONFIG_ARCH_WANT_OPTIMIZE_VMEMMAP >> -static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, >> - struct dev_pagemap *pgmap) >> +static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap, >> + struct dev_pagemap *pgmap) >> { >> - return is_power_of_2(sizeof(struct page)) && >> - pgmap && (pgmap_vmemmap_nr(pgmap) > 1) && !altmap; >> + if (pgmap) { >> + unsigned long nr_pages; >> + unsigned long nr_vmemmap_pages; >> + >> + nr_pages = pgmap_vmemmap_nr(pgmap); >> + nr_vmemmap_pages = ((nr_pages * sizeof(struct page)) >> PAGE_SHIFT); >> + /* >> + * For vmemmap optimization with DAX we need minimum 2 vmemmap > > > >> + * pages. See layout diagram in Documentation/mm/vmemmap_dedup.rst >> + */ >> + return is_power_of_2(sizeof(struct page)) && >> + (nr_vmemmap_pages > VMEMMAP_RESERVE_NR) && !altmap; >> + } > > It would be more readable (i.e. less identation) if you just reverse this: > > unsigned long nr_vmemmap_pages; > > if (!pgmap || !is_power_of_2(sizeof(struct page)) > return false; > > nr_vmemmap_pages = ((pgmap_vmemmap_nr(pgmap) * > sizeof(struct page)) >> PAGE_SHIFT); > > /* > * For vmemmap optimization with DAX we need minimum 2 vmemmap > * pages. See layout diagram in Documentation/mm/vmemmap_dedup.rst > */ > return (nr_vmemmap_pages > VMEMMAP_RESERVE_NR) && !altmap; > > Will update >> + return false; >> } >> +/* >> + * If we don't have an architecture override, use the generic rule >> + */ >> +#ifndef vmemmap_can_optimize >> +#define vmemmap_can_optimize __vmemmap_can_optimize >> +#endif >> + > > sparse-vmemmap code is trivial to change to use dedup a single vmemmap page > (e.g. to align with hugetlb), hopefully the architecture override to do. this is > to say whether VMEMMAP_RESERVE_NR should have similar to above? VMEMMAP_RESERVE_NR was added to avoid the usage of `2` in the below code. The reason we need the arch override was to add an additional check on ppc64 as shown by patch https://lore.kernel.org/linux-mm/20230616110826.344417-16-aneesh.kumar@linux.ibm.com/ bool vmemmap_can_optimize(struct vmem_altmap *altmap, struct dev_pagemap *pgmap) { if (radix_enabled()) return __vmemmap_can_optimize(altmap, pgmap); return false; } > >> #else >> static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, >> struct dev_pagemap *pgmap) >> diff --git a/mm/mm_init.c b/mm/mm_init.c >> index 7f7f9c677854..d1676afc94f1 100644 >> --- a/mm/mm_init.c >> +++ b/mm/mm_init.c >> @@ -1020,7 +1020,7 @@ static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, >> if (!vmemmap_can_optimize(altmap, pgmap)) >> return pgmap_vmemmap_nr(pgmap); >> >> - return 2 * (PAGE_SIZE / sizeof(struct page)); >> + return VMEMMAP_RESERVE_NR * (PAGE_SIZE / sizeof(struct page)); >> } >> >> static void __ref memmap_init_compound(struct page *head,
diff --git a/include/linux/mm.h b/include/linux/mm.h index 27ce77080c79..9a45e61cd83f 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -31,6 +31,8 @@ #include <linux/memremap.h> #include <linux/slab.h> +#include <asm/page.h> + struct mempolicy; struct anon_vma; struct anon_vma_chain; @@ -3550,13 +3552,33 @@ void vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *altmap); #endif +#define VMEMMAP_RESERVE_NR 2 #ifdef CONFIG_ARCH_WANT_OPTIMIZE_VMEMMAP -static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, - struct dev_pagemap *pgmap) +static inline bool __vmemmap_can_optimize(struct vmem_altmap *altmap, + struct dev_pagemap *pgmap) { - return is_power_of_2(sizeof(struct page)) && - pgmap && (pgmap_vmemmap_nr(pgmap) > 1) && !altmap; + if (pgmap) { + unsigned long nr_pages; + unsigned long nr_vmemmap_pages; + + nr_pages = pgmap_vmemmap_nr(pgmap); + nr_vmemmap_pages = ((nr_pages * sizeof(struct page)) >> PAGE_SHIFT); + /* + * For vmemmap optimization with DAX we need minimum 2 vmemmap + * pages. See layout diagram in Documentation/mm/vmemmap_dedup.rst + */ + return is_power_of_2(sizeof(struct page)) && + (nr_vmemmap_pages > VMEMMAP_RESERVE_NR) && !altmap; + } + return false; } +/* + * If we don't have an architecture override, use the generic rule + */ +#ifndef vmemmap_can_optimize +#define vmemmap_can_optimize __vmemmap_can_optimize +#endif + #else static inline bool vmemmap_can_optimize(struct vmem_altmap *altmap, struct dev_pagemap *pgmap) diff --git a/mm/mm_init.c b/mm/mm_init.c index 7f7f9c677854..d1676afc94f1 100644 --- a/mm/mm_init.c +++ b/mm/mm_init.c @@ -1020,7 +1020,7 @@ static inline unsigned long compound_nr_pages(struct vmem_altmap *altmap, if (!vmemmap_can_optimize(altmap, pgmap)) return pgmap_vmemmap_nr(pgmap); - return 2 * (PAGE_SIZE / sizeof(struct page)); + return VMEMMAP_RESERVE_NR * (PAGE_SIZE / sizeof(struct page)); } static void __ref memmap_init_compound(struct page *head,
dax vmemmap optimization requires a minimum of 2 PAGE_SIZE area within vmemmap such that tail page mapping can point to the second PAGE_SIZE area. Enforce that in vmemmap_can_optimize() function. Architectures like powerpc also want to enable vmemmap optimization conditionally (only with radix MMU translation). Hence allow architecture override. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> --- include/linux/mm.h | 30 ++++++++++++++++++++++++++---- mm/mm_init.c | 2 +- 2 files changed, 27 insertions(+), 5 deletions(-)