Re: [Xen-devel] Dirtied pages in Xen's shadow page tables

[Khoa Huynh <khoa@xxxxxxxxxx>]

xen-devel-bounces@xxxxxxxxxxxxxxxxxxx wrote on 12/01/2005 10:03:37 PM:

> Hi All,
>     I am trying to come up with a matrix that gives the information
> about the Xen's pages that are frequently dirtied. For this, I am
> going to use the shadow page tables. In [unstable]/arch/x86/mm.c, it
> is mentioned that these is a reference counting of pages and each
> page has two refcounts: tot_count and type_count(line No. 29 to 45).
>     But I didnt found these two refcounts being used anywhere else
> in the code. Can anybody please tell me where I can find this
> information or guide me in appropriate direction.
> Thank you very much for your time and consideration. It will be a
> great help to me,
>
> Neeta.

For each page, there are two refcounts: the usual reference count
and the type reference count.  These refcounts are defined in pfn_info
structure in xen/include/asm-x86/mm.h:

struct pfn_info *page;
page->count_info is the page reference count
page->u.inuse.type_info is the page type reference count

The page reference count is incremented and decremented in get_page()
and put_page(), respectively.  Both of these are defined in
xen/include/asm-x86/mm.h.

The page type reference count is incremented and decremented in
get_page_type() and put_page_type(), respectively.  Both of these
are defined in xen/arch/x86/mm.c.

In addition, in shadow page table mode, these reference counts
are manipulated in shadow_get_page* () and shadow_put_page* ().

Hope this helps.  Thanks.

Regards,
Khoa



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