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    SubjectRe: Regression - locking (all from 2.6.28)
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    On Wed, 2009-03-04 at 16:54 -0800, Dave Hansen wrote:
    > On Tue, 2009-03-03 at 15:01 +0000, Catalin Marinas wrote:
    > > > + /* mem_map scanning */
    > > > + for_each_online_node(i) {
    > > > + struct page *page, *end;
    > > > +
    > > > + page = NODE_MEM_MAP(i);
    > > > + end = page + NODE_DATA(i)->node_spanned_pages;
    > > > +
    > > > + scan_block(page, end, NULL);
    > > > + }
    [...]
    > One completely unoptimized thing you can do which will scan a 'struct
    > page' at a time is this:
    >
    > for_each_online_node(i) {
    > unsigned long pfn;
    > for (pfn = node_start_pfn(i); pfn < node_end_pfn(i); pfn++) {
    > struct page *page;
    > if (!pfn_valid(pfn))
    > continue;
    > page = pfn_to_page(pfn);
    > scan_block(page, page+1, NULL);
    > }
    > }

    It seems that node_start_pfn() isn't present on all the architectures. I
    ended up with something like below:

    + /* struct page scanning for each node */
    + for_each_online_node(i) {
    + pg_data_t *pgdat = NODE_DATA(i);
    + unsigned long start_pfn = pgdat->node_start_pfn;
    + unsigned long end_pfn = start_pfn +
    + pgdat->node_spanned_pages - 1;
    + unsigned long pfn;
    +
    + for (pfn = start_pfn; pfn < end_pfn; pfn++) {
    + struct page *page;
    +
    + if (!pfn_valid(pfn))
    + continue;
    + page = pfn_to_page(pfn);
    + /* only scan if page is in use */
    + if (page_count(page) == 0)
    + continue;
    + scan_block(page, page + 1, NULL);
    + }
    + }

    Are the pgdat->node_start_pfn and pgdat->node_spanned_pages always
    valid? Thanks.

    --
    Catalin



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