Re: [PATCH v4 03/13] mm/vmemmap: Improve vmemmap_can_optimize and allow architectures to override
From: Christophe Leroy <hidden>
Date: 2023-07-10 17:20:57
Also in:
linux-mm
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 <redacted>
Reviewed-by: Christophe Leroy <redacted> 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() ?
quoted hunk ↗ jump to hunk
--- 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,