Re : sparsemem usage

From: moreau francis
Date: Thu Aug 10 2006 - 08:38:29 EST

KAMEZAWA Hiroyuki wrote:
> On Wed, 9 Aug 2006 14:19:01 +0000 (GMT)
> moreau francis <francis_moreau2000@xxxxxxxx> wrote:
>> Not all arch have page_is_ram(). OK it should be easy to have but we will
>> need create new data structures to keep this info. The point is that it's
>> really easy for memory model such sparsemem to keep this info.
>>> Do you have a usage model in which we really care about the number of
>>> pages in the system to that level of accuracy?
>> show_mem(), which is arch specific, needs to report them. And some
>> implementations use only pfn_valid().
> BTW, ioresouce information (see kernel/resouce.c)
> [kamezawa@aworks Development]$ cat /proc/iomem | grep RAM
> 00000000-0009fbff : System RAM
> 000a0000-000bffff : Video RAM area
> 00100000-2dfeffff : System RAM
> is not enough ?

well actually you show that to get a really simple information, ie does
a page exist ?, we need to parse some kernel data structures like
ioresource (which is, IMHO, hackish) or duplicate in each architecture
some data to keep track of existing pages.

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