linux-kernel - Re: [PATCH 2/6] mm/page_alloc.c: simplify the code by using macro K()

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Message-ID: <03653d41-abe0-46f0-9eee-28cad9f5edea@huawei.com>
Date:   Wed, 1 Sep 2021 15:37:49 +0800
From:   Miaohe Lin <linmiaohe@...wei.com>
To:     Oleksandr Natalenko <oleksandr@...alenko.name>
CC:     <vbabka@...e.cz>, <sfr@...b.auug.org.au>, <peterz@...radead.org>,
        <mgorman@...hsingularity.net>, <linux-mm@...ck.org>,
        <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/6] mm/page_alloc.c: simplify the code by using macro K()

On 2021/8/31 22:19, Oleksandr Natalenko wrote:
> Hello.
> 
> On úterý 31. srpna 2021 13:08:42 CEST Miaohe Lin wrote:
>> On 2021/8/31 16:54, Oleksandr Natalenko wrote:
>>> Hello.
>>>
>>> On pondělí 30. srpna 2021 16:10:47 CEST Miaohe Lin wrote:
>>>> Use helper macro K() to convert the pages to the corresponding size.
>>>> Minor readability improvement.
>>>>
>>>> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
>>>> ---
>>>>
>>>>  mm/page_alloc.c | 12 +++++-------
>>>>  1 file changed, 5 insertions(+), 7 deletions(-)
>>>>
>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>>>> index dbb3338d9287..d3983244f56f 100644
>>>> --- a/mm/page_alloc.c
>>>> +++ b/mm/page_alloc.c
>>>> @@ -8134,8 +8134,7 @@ unsigned long free_reserved_area(void *start, void
>>>> *end, int poison, const char }
>>>>
>>>>  	if (pages && s)
>>>>
>>>> -		pr_info("Freeing %s memory: %ldK\n",
>>>> -			s, pages << (PAGE_SHIFT - 10));
>>>> +		pr_info("Freeing %s memory: %ldK\n", s, K(pages));
>>>>
>>>>  	return pages;
>>>>  
>>>>  }
>>>>
>>>> @@ -8180,14 +8179,13 @@ void __init mem_init_print_info(void)
>>>>
>>>>  		", %luK highmem"
>>>>  
>>>>  #endif
>>>>  
>>>>  		")\n",
>>>>
>>>> -		nr_free_pages() << (PAGE_SHIFT - 10),
>>>> -		physpages << (PAGE_SHIFT - 10),
>>>> +		K(nr_free_pages()), K(physpages),
>>>>
>>>>  		codesize >> 10, datasize >> 10, rosize >> 10,
>>>>  		(init_data_size + init_code_size) >> 10, bss_size >> 10,
>>>>
>>>> -		(physpages - totalram_pages() - totalcma_pages) << (PAGE_SHIFT
>>>
>>> - 10),
>>>
>>>> -		totalcma_pages << (PAGE_SHIFT - 10)
>>>> +		K(physpages - totalram_pages() - totalcma_pages),
>>>> +		K(totalcma_pages)
>>>>
>>>>  #ifdef	CONFIG_HIGHMEM
>>>>
>>>> -		, totalhigh_pages() << (PAGE_SHIFT - 10)
>>>> +		, K(totalhigh_pages())
>>>>
>>>>  #endif
>>>>  
>>>>  		);
>>>>  
>>>>  }
>>>
>>> (my concern is not quite within the scope of this submission, but I'll ask
>>> anyway)
>>>
>>> Given we have this:
>>>
>>> ```
>>> git grep '#define K(x)' v5.14
>>> v5.14:drivers/base/node.c:#define K(x) ((x) << (PAGE_SHIFT - 10))
>>> v5.14:drivers/net/hamradio/scc.c:#define K(x) kiss->x
>>> v5.14:kernel/debug/kdb/kdb_main.c:#define K(x) ((x) << (PAGE_SHIFT - 10))
>>> v5.14:mm/backing-dev.c:#define K(x) ((x) << (PAGE_SHIFT - 10))
>>> v5.14:mm/memcontrol.c:#define K(x) ((x) << (PAGE_SHIFT-10))
>>> v5.14:mm/oom_kill.c:#define K(x) ((x) << (PAGE_SHIFT-10))
>>> v5.14:mm/page_alloc.c:#define K(x) ((x) << (PAGE_SHIFT-10))
>>> ```
>>>
>>> Shouldn't this macro go to some header file instead to get rid of define
>>> repetitions?
>>
>> Many thanks for figuring this out. I think we should get rid of these
>> repetitions too. But I'am not sure where this definition should be. Any
>> suggestion? Thanks.
> 
> I'm not sure what place suits best. At first I thought maybe linux/mm.h or 
> linux/mm_inline.h, but since PAGE_SHIFT is declared in asm-generic/page.h, 
> probably K(x) can also go there as well?

K(x) is relevant with PAGE_SHIFT. So I think K(x) can also go asm-generic/page.h too.
Am I supposed to do this when free or will you kindly do this?

Many thanks.

>