Re: [PATCH v4 03/13] mm/vmemmap: Improve vmemmap_can_optimize and allow architectures to override
Christophe Leroy writes: > Le 10/07/2023 à 18:08, Aneesh Kumar K.V a écrit : >> 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 > > Reviewed-by: Christophe Leroy > > Why renaming vmemmap_can_optimize() to __vmemmap_can_optimize() and keep > it when vmemmap_can_optimize() has been override ? Is that because you > expect overriding version of vmemmap_can_optimize() to call > __vmemmap_can_optimize() ? > Yes, __vmemap_can_optimize will be used in patch 11 https://lore.kernel.org/linuxppc-dev/20230710160842.56300-12-aneesh.ku...@linux.ibm.com -aneesh
Re: [PATCH v4 03/13] mm/vmemmap: Improve vmemmap_can_optimize and allow architectures to override
Le 10/07/2023 à 18:08, Aneesh Kumar K.V a écrit :
> 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
Reviewed-by: Christophe Leroy
Why renaming vmemmap_can_optimize() to __vmemmap_can_optimize() and keep
it when vmemmap_can_optimize() has been override ? Is that because you
expect overriding version of vmemmap_can_optimize() to call
__vmemmap_can_optimize() ?
> ---
> include/linux/mm.h | 27 +++
> mm/mm_init.c | 2 +-
> 2 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 2dd73e4f3d8e..1a2234ee14d2 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -3639,13 +3639,32 @@ 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;
> + unsigned long nr_pages;
> + unsigned long nr_vmemmap_pages;
> +
> + if (!pgmap || !is_power_of_2(sizeof(struct page)))
> + return false;
> +
> + 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 !altmap && (nr_vmemmap_pages > VMEMMAP_RESERVE_NR);
> }
> +/*
> + * 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 a1963c3322af..245ac69b66a5 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,
[PATCH v4 03/13] mm/vmemmap: Improve vmemmap_can_optimize and allow architectures to override
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
---
include/linux/mm.h | 27 +++
mm/mm_init.c | 2 +-
2 files changed, 24 insertions(+), 5 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2dd73e4f3d8e..1a2234ee14d2 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3639,13 +3639,32 @@ 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;
+ unsigned long nr_pages;
+ unsigned long nr_vmemmap_pages;
+
+ if (!pgmap || !is_power_of_2(sizeof(struct page)))
+ return false;
+
+ 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 !altmap && (nr_vmemmap_pages > VMEMMAP_RESERVE_NR);
}
+/*
+ * 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 a1963c3322af..245ac69b66a5 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,
--
2.41.0
