[RFC PATCH 14/15] mm: introduce MIN_MAX_ORDER to replace MAX_ORDER as compile time constant.
Zi Yan
ziy at nvidia.com
Mon Aug 9 08:35:39 PDT 2021
On 8 Aug 2021, at 4:23, Mike Rapoport wrote:
> On Thu, Aug 05, 2021 at 03:02:52PM -0400, Zi Yan wrote:
>> From: Zi Yan <ziy at nvidia.com>
>>
>> For other MAX_ORDER uses (described below), there is no need or too much
>> hassle to convert certain static array to dynamic ones. Add
>> MIN_MAX_ORDER to serve as compile time constant in place of MAX_ORDER.
>>
>> ARM64 hypervisor maintains its own free page list and does not import
>> any core kernel symbols, so soon-to-be runtime variable MAX_ORDER is not
>> accessible in ARM64 hypervisor code. Also there is no need to allocating
>> very large pages.
>>
>> In SLAB/SLOB/SLUB, 2-D array kmalloc_caches uses MAX_ORDER in its second
>> dimension. It is too much hassle to allocate memory for kmalloc_caches
>> before any proper memory allocator is set up.
>>
>> Signed-off-by: Zi Yan <ziy at nvidia.com>
>> Cc: Marc Zyngier <maz at kernel.org>
>> Cc: Catalin Marinas <catalin.marinas at arm.com>
>> Cc: Christoph Lameter <cl at linux.com>
>> Cc: Vlastimil Babka <vbabka at suse.cz>
>> Cc: Quentin Perret <qperret at google.com>
>> Cc: linux-arm-kernel at lists.infradead.org
>> Cc: kvmarm at lists.cs.columbia.edu
>> Cc: linux-mm at kvack.org
>> Cc: linux-kernel at vger.kernel.org
>> ---
>> arch/arm64/kvm/hyp/include/nvhe/gfp.h | 2 +-
>> arch/arm64/kvm/hyp/nvhe/page_alloc.c | 3 ++-
>> include/linux/mmzone.h | 3 +++
>> include/linux/slab.h | 8 ++++----
>> mm/slab.c | 2 +-
>> mm/slub.c | 7 ++++---
>> 6 files changed, 15 insertions(+), 10 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/hyp/include/nvhe/gfp.h b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
>> index fb0f523d1492..c774b4a98336 100644
>> --- a/arch/arm64/kvm/hyp/include/nvhe/gfp.h
>> +++ b/arch/arm64/kvm/hyp/include/nvhe/gfp.h
>> @@ -16,7 +16,7 @@ struct hyp_pool {
>> * API at EL2.
>> */
>> hyp_spinlock_t lock;
>> - struct list_head free_area[MAX_ORDER];
>> + struct list_head free_area[MIN_MAX_ORDER];
>> phys_addr_t range_start;
>> phys_addr_t range_end;
>> unsigned short max_order;
>> diff --git a/arch/arm64/kvm/hyp/nvhe/page_alloc.c b/arch/arm64/kvm/hyp/nvhe/page_alloc.c
>> index 41fc25bdfb34..a1cc1b648de0 100644
>> --- a/arch/arm64/kvm/hyp/nvhe/page_alloc.c
>> +++ b/arch/arm64/kvm/hyp/nvhe/page_alloc.c
>> @@ -226,7 +226,8 @@ int hyp_pool_init(struct hyp_pool *pool, u64 pfn, unsigned int nr_pages,
>> int i;
>>
>> hyp_spin_lock_init(&pool->lock);
>> - pool->max_order = min(MAX_ORDER, get_order(nr_pages << PAGE_SHIFT));
>> +
>> + pool->max_order = min(MIN_MAX_ORDER, get_order(nr_pages << PAGE_SHIFT));
>> for (i = 0; i < pool->max_order; i++)
>> INIT_LIST_HEAD(&pool->free_area[i]);
>> pool->range_start = phys;
>> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
>> index 09aafc05aef4..379dada82d4b 100644
>> --- a/include/linux/mmzone.h
>> +++ b/include/linux/mmzone.h
>> @@ -27,11 +27,14 @@
>> #ifndef CONFIG_ARCH_FORCE_MAX_ORDER
>> #ifdef CONFIG_SET_MAX_ORDER
>> #define MAX_ORDER CONFIG_SET_MAX_ORDER
>> +#define MIN_MAX_ORDER CONFIG_SET_MAX_ORDER
>> #else
>> #define MAX_ORDER 11
>> +#define MIN_MAX_ORDER MAX_ORDER
>> #endif /* CONFIG_SET_MAX_ORDER */
>> #else
>> #define MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
>> +#define MIN_MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
>> #endif /* CONFIG_ARCH_FORCE_MAX_ORDER */
>> #define MAX_ORDER_NR_PAGES (1 << (MAX_ORDER - 1))
>
> The end result of this #ifdef explosion looks entirely unreadable:
Just to clarify the use of #ifdef:
MAX_ORDER is changed to a boot time variable and it cannot be used
for static array declaration, so I added MIN_MAX_ORDER.
At the moment, there are three cases of setting MAX_ORDER and
MIN_MAX_ORDER:
1. CONFIG_ARCH_FORCE_MAX_ORDER tells the MAX_ORDER certain arch
needs at compilation time.
2. CONFIG_SET_MAX_ORDER allows to change MAX_ORDER when an arch
does not set its MAX_ORER and SPARSEMEM_VMEMMAP is set.
3. !SPARSEMEM_VMEMMAP and no CONFIG_ARCH_FORCE_MAX_ORDER, then
MAX_ORDER is set to 11 by default.
I agree the code is hard to read, I will clean this up.
>
> /* Free memory management - zoned buddy allocator. */
> #ifndef CONFIG_ARCH_FORCE_MAX_ORDER
> #ifdef CONFIG_SET_MAX_ORDER
> /* Defined in mm/page_alloc.c */
> extern int buddy_alloc_max_order;
>
> #define MAX_ORDER buddy_alloc_max_order
> #define MIN_MAX_ORDER CONFIG_SET_MAX_ORDER
> #else
> #define MAX_ORDER 11
> #define MIN_MAX_ORDER MAX_ORDER
> #endif /* CONFIG_SET_MAX_ORDER */
> #else
>
> #ifdef CONFIG_SPARSEMEM_VMEMMAP
> /* Defined in mm/page_alloc.c */
> extern int buddy_alloc_max_order;
>
> #define MAX_ORDER buddy_alloc_max_order
> #else
> #define MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
> #endif /* CONFIG_SPARSEMEM_VMEMMAP */
> #define MIN_MAX_ORDER CONFIG_ARCH_FORCE_MAX_ORDER
> #endif /* CONFIG_ARCH_FORCE_MAX_ORDER */
>
>> diff --git a/include/linux/slab.h b/include/linux/slab.h
>> index 2c0d80cca6b8..d8747c158db6 100644
>> --- a/include/linux/slab.h
>> +++ b/include/linux/slab.h
>> @@ -244,8 +244,8 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
>> * to do various tricks to work around compiler limitations in order to
>> * ensure proper constant folding.
>> */
>> -#define KMALLOC_SHIFT_HIGH ((MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
>> - (MAX_ORDER + PAGE_SHIFT - 1) : 25)
>> +#define KMALLOC_SHIFT_HIGH ((MIN_MAX_ORDER + PAGE_SHIFT - 1) <= 25 ? \
>> + (MIN_MAX_ORDER + PAGE_SHIFT - 1) : 25)
>> #define KMALLOC_SHIFT_MAX KMALLOC_SHIFT_HIGH
>> #ifndef KMALLOC_SHIFT_LOW
>> #define KMALLOC_SHIFT_LOW 5
>> @@ -258,7 +258,7 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
>> * (PAGE_SIZE*2). Larger requests are passed to the page allocator.
>> */
>> #define KMALLOC_SHIFT_HIGH (PAGE_SHIFT + 1)
>> -#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1)
>> +#define KMALLOC_SHIFT_MAX (MIN_MAX_ORDER + PAGE_SHIFT - 1)
>> #ifndef KMALLOC_SHIFT_LOW
>> #define KMALLOC_SHIFT_LOW 3
>> #endif
>> @@ -271,7 +271,7 @@ static inline void __check_heap_object(const void *ptr, unsigned long n,
>> * be allocated from the same page.
>> */
>> #define KMALLOC_SHIFT_HIGH PAGE_SHIFT
>> -#define KMALLOC_SHIFT_MAX (MAX_ORDER + PAGE_SHIFT - 1)
>> +#define KMALLOC_SHIFT_MAX (MIN_MAX_ORDER + PAGE_SHIFT - 1)
>> #ifndef KMALLOC_SHIFT_LOW
>> #define KMALLOC_SHIFT_LOW 3
>> #endif
>> diff --git a/mm/slab.c b/mm/slab.c
>> index d0f725637663..0041de8ec0e9 100644
>> --- a/mm/slab.c
>> +++ b/mm/slab.c
>> @@ -466,7 +466,7 @@ static int __init slab_max_order_setup(char *str)
>> {
>> get_option(&str, &slab_max_order);
>> slab_max_order = slab_max_order < 0 ? 0 :
>> - min(slab_max_order, MAX_ORDER - 1);
>> + min(slab_max_order, MIN_MAX_ORDER - 1);
>> slab_max_order_set = true;
>>
>> return 1;
>> diff --git a/mm/slub.c b/mm/slub.c
>> index b6c5205252eb..228e4a77c678 100644
>> --- a/mm/slub.c
>> +++ b/mm/slub.c
>> @@ -3564,8 +3564,9 @@ static inline int calculate_order(unsigned int size)
>> /*
>> * Doh this slab cannot be placed using slub_max_order.
>> */
>> - order = slab_order(size, 1, MAX_ORDER, 1);
>> - if (order < MAX_ORDER)
>> +
>> + order = slab_order(size, 1, MIN_MAX_ORDER, 1);
>> + if (order < MIN_MAX_ORDER)
>> return order;
>> return -ENOSYS;
>> }
>> @@ -4079,7 +4080,7 @@ __setup("slub_min_order=", setup_slub_min_order);
>> static int __init setup_slub_max_order(char *str)
>> {
>> get_option(&str, (int *)&slub_max_order);
>> - slub_max_order = min(slub_max_order, (unsigned int)MAX_ORDER - 1);
>> + slub_max_order = min(slub_max_order, (unsigned int)MIN_MAX_ORDER - 1);
>>
>> return 1;
>> }
>> --
>> 2.30.2
>>
>
> --
> Sincerely yours,
> Mike.
—
Best Regards,
Yan, Zi
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