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

[Gioh Kim]

2014-10-21 오후 10:21, PINTU KUMAR 쓴 글:
> 
> Hi,
> 
> ----- Original Message -----
>> From: Gioh Kim <gioh.kim@xxxxxxx>
>> To: Pintu Kumar <pintu.k@xxxxxxxxxxx>; akpm@xxxxxxxxxxxxxxxxxxxx;
> hannes@xxxxxxxxxxx; riel@xxxxxxxxxx; mgorman@xxxxxxx;
> vdavydov@xxxxxxxxxxxxx; nasa4836@xxxxxxxxx; ddstreet@xxxxxxxx;
> m.szyprowski@xxxxxxxxxxx; mina86@xxxxxxxxxx; iamjoonsoo.kim@xxxxxxx; aneesh.
> kumar@xxxxxxxxxxxxxxxxxx; lauraa@xxxxxxxxxxxxxx; rientjes@xxxxxxxxxx;
> vbabka@xxxxxxx; sasha.levin@xxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; linux-
> mm@xxxxxxxxx
>> Cc: cpgs@xxxxxxxxxxx; pintu_agarwal@xxxxxxxxx; vishnu.ps@xxxxxxxxxxx;
> rohit.kr@xxxxxxxxxxx; ed.savinay@xxxxxxxxxxx; 이건호 <gunho.lee@xxxxxxx>
>> Sent: Tuesday, 21 October 2014 6:17 AM
>> Subject: Re: [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@xxxxxxxxxxx>
>>> Signed-off-by: Vishnu Pratap Singh <vishnu.ps@xxxxxxxxxxx>
>>> ---
>>>    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
> 
> Ok, as per Andrew Morton comment, will remove CONFIG_CMA,
> But then I need to put it under: include/linux/mm.h
> In that case, it will solve the problem for CMA and non-CMA case.
> Because, mm.h is already included in cma.c
> 
>>>    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.
>>
> 
> Firstly, I want to move this to mm/page_alloc.c, so that it can be visible
> for non-CMA cases.
> Next, the purpose this variable is not only during init time.
> Just like totalram_pages, I wanted to retain this variable to use it to
> populate the CMA info, during /proc/meminfo.
> Like:
> CMATotal: (using totalcma_pages)
> CMAFree:  (using NR_FREE_CMA_PAGES)
> I will post these changes in the next patch series.
> Please let me know your comments.
> 
>>>    
>>>    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.
>>
> 
> Ok agree. If we move totalcma_pages declaration to page_alloc.c and mm.h,
> then we can get rid of CONFIG_CMA, to make it neat.
> 
> 
>> I'm not sure but I think there is a debugfs file for cma.
>> Can you use it?
>>
> 
> As of now, I think there is no debugfs for cma.
> However, we can make one if required.
> 
>> 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
>>
> 
> I think this is not required.
> For multiple CMA regions, this can be found under:
> /sys/kernel/debug/memblock/reserved

I'm sorry. I didn't know it.

> However, as I said, we can populate this information under: /proc/meminfo
> I think capturing it at one place will be better. For non-CMA cases, it
> will be hidden.
> Thus summary of CMA info can be seen in meminfo, and detailed information
> can be seen in memblock/reserved.

I agree with you.
I'm looking forward to your next patch.

> Do, let me know if you have any other idea?
> 
>>
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> 
> 
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