linux-kernel - Re: [PATCH v1] mm: page_alloc: Add debug log in free_reserved

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Message-ID: <1f6708d2-1ca8-6d1f-d9f0-855f2df755ed@codeaurora.org>
Date:   Wed, 29 Sep 2021 14:28:51 +0530
From:   Faiyaz Mohammed <faiyazm@...eaurora.org>
To:     David Hildenbrand <david@...hat.com>, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     guptap@...eaurora.org
Subject: Re: [PATCH v1] mm: page_alloc: Add debug log in free_reserved_area
 for static memory



On 9/28/2021 4:46 PM, David Hildenbrand wrote:
> On 28.09.21 12:53, Faiyaz Mohammed wrote:
>>
>>
>> On 9/28/2021 4:09 PM, David Hildenbrand wrote:
>>> On 28.09.21 11:04, Faiyaz Mohammed wrote:
>>>> For INITRD and initmem memory is reserved through "memblock_reserve"
>>>> during boot up but it is free via "free_reserved_area" instead
>>>> of "memblock_free".
>>>> For example:
>>>> [    0.294848] Freeing initrd memory: 12K.
>>>> [    0.696688] Freeing unused kernel memory: 4096K.
>>>>
>>>> To get the start and end address of the above freed memory and to
>>>> account
>>>> proper memblock added memblock_dbg log in "free_reserved_area".
>>>> After adding log:
>>>> [    0.294837] memblock_free: [0x00000083600000-0x00000083603000]
>>>> free_initrd_mem+0x20/0x28
>>>> [    0.294848] Freeing initrd memory: 12K.
>>>> [    0.695246] memblock_free: [0x00000081600000-0x00000081a00000]
>>>> free_initmem+0x70/0xc8
>>>> [    0.696688] Freeing unused kernel memory: 4096K.
>>>>
>>>> Signed-off-by: Faiyaz Mohammed <faiyazm@...eaurora.org>
>>>> ---
>>>>    mm/page_alloc.c | 5 +++++
>>>>    1 file changed, 5 insertions(+)
>>>>
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index b37435c..f85c3b2 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -8129,6 +8129,11 @@ unsigned long free_reserved_area(void *start,
>>>> void *end, int poison, const char
>>>>            pr_info("Freeing %s memory: %ldK\n",
>>>>                s, pages << (PAGE_SHIFT - 10));
>>>>    +#ifdef CONFIG_HAVE_MEMBLOCK
>>>> +        memblock_dbg("memblock_free: [%#016llx-%#016llx] %pS\n",
>>>> +            __pa(start), __pa(end), (void *)_RET_IP_);
>>>> +#endif
>>>
>>> IMHO, the "memblock_free" part is misleading. Something was allocated
>>> early via memblock, then we transitioned to the buddy, now we're freeing
>>> that early allocation via the buddy.
>>> Yes, we're freeing the early allocation via buddy, but for proper
>> memblock accounting we need this debug print.
>>
> 
> What do you mean with "accounting" ? These are debug statements.
> 
> 
Yes, these are debug statements, which help to know the a-b address
belongs to x callsite. This info is required when memblock=debug is
passed through command line and CONFIG_HAVE_MEMBLOCK is enabled.

Thanks,
Mohammed Faiyaz