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SubjectRe: [PATCH] mm: cma: split cma-reserved in dmesg log


2014-10-20 오후 4:33, Pintu Kumar 쓴 글:
> When the system boots up, in the dmesg logs we can see
> the memory statistics along with total reserved as below.
> Memory: 458840k/458840k available, 65448k reserved, 0K highmem
>
> When CMA is enabled, still the total reserved memory remains the same.
> However, the CMA memory is not considered as reserved.
> But, when we see /proc/meminfo, the CMA memory is part of free memory.
> This creates confusion.
> This patch corrects the problem by properly substracting the CMA reserved
> memory from the total reserved memory in dmesg logs.
>
> Below is the dmesg snaphot from an arm based device with 512MB RAM and
> 12MB single CMA region.
>
> Before this change:
> Memory: 458840k/458840k available, 65448k reserved, 0K highmem
>
> After this change:
> Memory: 458840k/458840k available, 53160k reserved, 12288k cma-reserved, 0K highmem
>
> Signed-off-by: Pintu Kumar <pintu.k@samsung.com>
> Signed-off-by: Vishnu Pratap Singh <vishnu.ps@samsung.com>
> ---
> include/linux/swap.h | 3 +++
> mm/cma.c | 2 ++
> mm/page_alloc.c | 8 ++++++++
> 3 files changed, 13 insertions(+)
>
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 37a585b..beb84be 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -295,6 +295,9 @@ static inline void workingset_node_shadows_dec(struct radix_tree_node *node)
> /* linux/mm/page_alloc.c */
> extern unsigned long totalram_pages;
> extern unsigned long totalreserve_pages;
> +#ifdef CONFIG_CMA
> +extern unsigned long totalcma_pages;
> +#endif
> extern unsigned long dirty_balance_reserve;
> extern unsigned long nr_free_buffer_pages(void);
> extern unsigned long nr_free_pagecache_pages(void);
> diff --git a/mm/cma.c b/mm/cma.c
> index 963bc4a..73fe7be 100644
> --- a/mm/cma.c
> +++ b/mm/cma.c
> @@ -45,6 +45,7 @@ struct cma {
> static struct cma cma_areas[MAX_CMA_AREAS];
> static unsigned cma_area_count;
> static DEFINE_MUTEX(cma_mutex);
> +unsigned long totalcma_pages __read_mostly;

I think __read_mostly is not good here.
Cma areas often are rare
but we cannot expect how many cma areas exists.

>
> phys_addr_t cma_get_base(struct cma *cma)
> {
> @@ -288,6 +289,7 @@ int __init cma_declare_contiguous(phys_addr_t base,
> if (ret)
> goto err;
>
> + totalcma_pages += (size / PAGE_SIZE);
> pr_info("Reserved %ld MiB at %08lx\n", (unsigned long)size / SZ_1M,
> (unsigned long)base);
> return 0;
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index dd73f9a..c6165ac 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5521,6 +5521,9 @@ void __init mem_init_print_info(const char *str)
> pr_info("Memory: %luK/%luK available "
> "(%luK kernel code, %luK rwdata, %luK rodata, "
> "%luK init, %luK bss, %luK reserved"
> +#ifdef CONFIG_CMA
> + ", %luK cma-reserved"
> +#endif
> #ifdef CONFIG_HIGHMEM
> ", %luK highmem"
> #endif
> @@ -5528,7 +5531,12 @@ void __init mem_init_print_info(const char *str)
> nr_free_pages() << (PAGE_SHIFT-10), physpages << (PAGE_SHIFT-10),
> codesize >> 10, datasize >> 10, rosize >> 10,
> (init_data_size + init_code_size) >> 10, bss_size >> 10,
> +#ifdef CONFIG_CMA
> + (physpages - totalram_pages - totalcma_pages) << (PAGE_SHIFT-10),
> + totalcma_pages << (PAGE_SHIFT-10),
> +#else
> (physpages - totalram_pages) << (PAGE_SHIFT-10),
> +#endif
> #ifdef CONFIG_HIGHMEM
> totalhigh_pages << (PAGE_SHIFT-10),
> #endif
>

I basically agree with your point.
But CMA feature is not popular yet, so memory develoers probably doesn't like this.

I'm not sure but I think there is a debugfs file for cma.
Can you use it?

Or what do you think about making another proc file to show cma area size and address?
For instance,

# cat /proc/cmainfo
CMATotal: 400kB
0x10000000 300kB
0x20000000 100kB

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