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

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Message-ID: <ab7a9fb0-a3e7-0cb8-6dbd-40a68e6fd299@redhat.com>
Date:   Tue, 28 Sep 2021 13:16:38 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Faiyaz Mohammed <faiyazm@...eaurora.org>,
        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 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.


-- 
Thanks,

David / dhildenb