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    SubjectRe: [Approach #2] [RFC][PATCH] Remove cgroup member from struct page
    Dave Hansen wrote:
    > On Tue, 2008-09-09 at 18:20 -0700, Balbir Singh wrote:
    >> + start = pgdat->node_start_pfn;
    >> + end = pgdat->node_start_pfn + pgdat->node_spanned_pages;
    >> + size = (end - start) * sizeof(struct page_cgroup);
    >> + printk("Allocating %lu bytes for node %d\n", size, n);
    >> + pcg_map[n] = alloc_bootmem_node(pgdat, size);
    >> + /*
    >> + * We can do smoother recovery
    >> + */
    >> + BUG_ON(!pcg_map[n]);
    >> + return 0;
    >> }
    >
    > This will really suck for sparse memory machines. Imagine a machine
    > with 1GB of memory at 0x0 and another 1GB of memory at 1TB up in the
    > address space.
    >

    I would hate to re-implement the entire sparsemem code :(
    Kame did suggest making the memory controller depend on sparsemem (to hook in
    from there for allocations)

    > You also need to consider how it works with memory hotplug and how
    > you're going to grow it at runtime.
    >

    Yes, true. This is not the final version, a very very early version that I
    posted for initial comments.

    > Oh, and doesn't alloc_bootmem() panic() if it fails internally anyway?
    >
    > I need to look at your other approach. :)

    We'll need some slab_is_available() sort of checks that sparse.c uses and also
    deal with memory hotplug add and remove.

    --
    Balbir


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