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    SubjectRe: Re : Re : sparsemem usage
    moreau francis wrote:
    > Alan Cox wrote:
    >> Mapping out parts of a section is quite normal - think about the 640K to
    >> 1Mb hole in PC memory space.
    > OK. But I'm still worry. Please consider the following code
    > for (...; ...; ...) {
    > [...]
    > if (pfn_valid(i))
    > num_physpages++;
    > [...]
    > }
    > In that case num_physpages won't store an accurate value. Still it will be
    > used by the kernel to make some statistic assumptions on other kernel
    > data structure sizes.

    That would be incorrect usage. pfn_valid() simply doesn't tell you if
    you have memory backing a pfn, it mearly means you can interrogate the
    page* for it. A good example of code which counts pages in a region is
    in count_highmem_pages() which has a form as below:

    for (pfn = start; pfn < end; pfn++) {
    if (!pfn_valid(pfn))
    page = pfn_to_page(pfn);
    if (PageReserved(page))

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      Last update: 2006-08-03 11:51    [W:0.024 / U:0.716 seconds]
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