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Mon, 11 Oct 2021 06:50:01 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 smtp.codeaurora.org 70D17C4338F Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=fail smtp.mailfrom=codeaurora.org Subject: Re: [PATCH v1] mm: page_alloc: Add debug log in free_reserved_area for static memory To: David Hildenbrand , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: guptap@codeaurora.org References: <1632819849-511-1-git-send-email-faiyazm@codeaurora.org> <248ec931-7c16-3e2d-cc8f-8ce0dd4e923b@redhat.com> <0149edd5-fe7f-2786-413c-6de2eab3e30c@codeaurora.org> <1f6708d2-1ca8-6d1f-d9f0-855f2df755ed@codeaurora.org> <88df48af-901b-5765-d92c-6d14c2b1f73e@codeaurora.org> From: Faiyaz Mohammed Message-ID: Date: Mon, 11 Oct 2021 12:19:58 +0530 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/6/2021 5:48 PM, David Hildenbrand wrote: > On 06.10.21 14:13, Faiyaz Mohammed wrote: >> Hi, >> >> Sorry for delayed response. >> >> On 9/29/2021 10:33 PM, David Hildenbrand wrote: >>> On 29.09.21 10:58, Faiyaz Mohammed wrote: >>>> >>>> >>>> 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 >>>>>>>> --- >>>>>>>>      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. >>> >>> The issue I'm having is talking in the name of memblock "memblock_dbg, >>> memblock_free", when memblock might no longer be around. We have other >>> places where we free early memblock allocations back to the buddy. >> I didn't find place where we free early memblock allocation back to the >> buddy. > > One example I know is > > section_deactivate()->free_map_bootmem()->vmemmap_free()-> ... > free_pagetable()->free_reserved_page(). > > when we free the vmemmap allocated via memblock back to the buddy. > >> >> Why "memblock_dbg" print with "memblock_free" string?. >> - After buddy took over, buddy will free memblock reserved memory >> through free_reserved_area and it will print the freed memory size, but >> the freed memory through buddy still be part of >> memblock.reserved.regions. >> - To know the address ranges, added the "memblock_dbg" print along with >> "membloc_free" string. >> - If it is misleading or confusing, we can remove the "memblock_free" >> string from the "memblock_dgb" print and we can just print the address >> range when "memlock=debug" pass through command line. > > That would be better, but do we really have to depend on > "memlock=debug"? Can't we do pr_debug() ? > Yes, I think we can do pr_debug. I will update the patch and push again. Thanks and regards, Mohammed Faiyaz