LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: Dave Hansen <dave@linux.vnet.ibm.com>
To: KyongHo Cho <pullip.cho@samsung.com>
Cc: linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org, linux-samsung-soc@vger.kernel.org,
	Kukjin Kim <kgene.kim@samsung.com>,
	Ilho Lee <ilho215.lee@samsung.com>,
	KeyYoung Park <keyyoung.park@samsung.com>
Subject: Re: [PATCH] ARM: mm: Regarding section when dealing with meminfo
Date: Thu, 20 Jan 2011 09:20:47 -0800	[thread overview]
Message-ID: <1295544047.9039.609.camel@nimitz> (raw)
In-Reply-To: <1295516739-9839-1-git-send-email-pullip.cho@samsung.com>

On Thu, 2011-01-20 at 18:45 +0900, KyongHo Cho wrote:
> Sparsemem allows that a bank of memory spans over several adjacent
> sections if the start address and the end address of the bank
> belong to different sections.
> When gathering statictics of physical memory in mem_init() and
> show_mem(), this possiblity was not considered.
> 
> This patch guarantees that simple increasing the pointer to page
> descriptors does not exceed the boundary of a section
...
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 57c4c5c..6ccecbe 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -93,24 +93,38 @@ void show_mem(void)
> 
>  		pfn1 = bank_pfn_start(bank);
>  		pfn2 = bank_pfn_end(bank);
> -
> +#ifndef CONFIG_SPARSEMEM
>  		page = pfn_to_page(pfn1);
>  		end  = pfn_to_page(pfn2 - 1) + 1;
> -
> +#else
> +		pfn2--;
>  		do {
> -			total++;
> -			if (PageReserved(page))
> -				reserved++;
> -			else if (PageSwapCache(page))
> -				cached++;
> -			else if (PageSlab(page))
> -				slab++;
> -			else if (!page_count(page))
> -				free++;
> -			else
> -				shared += page_count(page) - 1;
> -			page++;
> -		} while (page < end);
> +			page = pfn_to_page(pfn1);
> +			if (pfn_to_section_nr(pfn1) < pfn_to_section_nr(pfn2)) {
> +				pfn1 += PAGES_PER_SECTION;
> +				pfn1 &= PAGE_SECTION_MASK;
> +			} else {
> +				pfn1 = pfn2;
> +			}
> +			end = pfn_to_page(pfn1) + 1;
> +#endif

This problem actually exists without sparsemem, too.  Discontigmem (at
least) does it as well.

The x86 version of show_mem() actually manages to do this without any
#ifdefs, and works for a ton of configuration options.  It uses
pfn_valid() to tell whether it can touch a given pfn.

Long-term, it might be a good idea to convert arm's show_mem() over to
use pgdat's like everything else.  But, for now, you should just be able
to do something roughly like this:

-               page = pfn_to_page(pfn1);
-               end  = pfn_to_page(pfn2 - 1) + 1;
-
-               do {
+		for (pfn = pfn1; pfn < pfn2; pfn++) {
+			if (!pfn_valid(pfn))
+				continue;
+			page = pfn_to_page(pfn);
+
                        total++;
                        if (PageReserved(page))
                                reserved++;
                        else if (PageSwapCache(page))
                                cached++;
                        else if (PageSlab(page))
                                slab++;
                        else if (!page_count(page))
                                free++;
                        else
                                shared += page_count(page) - 1;
                        page++;
-               } while (page < end);
+		}

That should work for sparsemem, or any other crazy memory models that we
come up with.  pfn_to_page() is pretty quick, especially when doing it
in a tight loop like that.

-- Dave


  parent reply	other threads:[~2011-01-20 17:22 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-01-20  9:45 KyongHo Cho
2011-01-20 14:28 ` Minchan Kim
2011-01-20 17:25   ` Dave Hansen
     [not found]   ` <AANLkTinXAiShaf1f69ufVHg7KPaY5j=jmOTtK71GNNp5@mail.gmail.com>
2011-01-20 17:43     ` Minchan Kim
2011-01-20 17:44       ` Minchan Kim
2011-01-20 17:52         ` KyongHo Cho
2011-01-20 17:20 ` Dave Hansen [this message]
     [not found]   ` <AANLkTi=nsAOtLPK75Wy5Rm8pfWob8xTP5259DyYuxR9J@mail.gmail.com>
2011-01-20 17:48     ` KyongHo Cho
2011-01-20 18:04     ` Dave Hansen
2011-01-20 18:01   ` Russell King - ARM Linux
2011-01-20 18:11     ` Dave Hansen
2011-01-23 18:05       ` Russell King - ARM Linux
2011-01-24 16:52         ` Dave Hansen
2011-01-24 17:58           ` Russell King - ARM Linux
2011-01-24 18:47             ` Dave Hansen
2011-01-25  0:33             ` KyongHo Cho
2011-01-21  2:12     ` KyongHo Cho
2011-01-21 10:38       ` Russell King - ARM Linux
2011-01-21 11:15         ` KyongHo Cho

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1295544047.9039.609.camel@nimitz \
    --to=dave@linux.vnet.ibm.com \
    --cc=ilho215.lee@samsung.com \
    --cc=keyyoung.park@samsung.com \
    --cc=kgene.kim@samsung.com \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linux-samsung-soc@vger.kernel.org \
    --cc=pullip.cho@samsung.com \
    --subject='Re: [PATCH] ARM: mm: Regarding section when dealing with meminfo' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).