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    SubjectRe: [PATCH] kthread: NUMA aware kthread_create_on_cpu()
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    Le lundi 29 novembre 2010 à 00:01 +0100, Andi Kleen a écrit :
    > On Sun, Nov 28, 2010 at 11:51:51PM +0100, Eric Dumazet wrote:
    > > > Also this messes up the policy of the caller process. You really
    > > > need to save/restore it.
    > >
    > > Well, caller process duty is to create kthreads in a loop.
    >
    > In this case any other allocations it may do
    > are still on those
    > nodes.

    As I said, it does only create_kthread() calls, and no "other
    allocations".

    while (!list_empty(&kthread_create_list)) {
    struct kthread_create_info *create;

    create = list_entry(kthread_create_list.next,
    struct kthread_create_info, list);
    list_del_init(&create->list);
    spin_unlock(&kthread_create_lock);

    create_kthread(create);

    spin_lock(&kthread_create_lock);
    }





    >
    > > > Problem is that this ends up in architecture specific code
    > > > for the stack, so may be a larger patch.
    > >
    > > I suggest arches that need slab to allocate kthread stacks do the
    > > appropriate changes, because I am not able to make them myself.
    > >
    > > On x86, we use page allocator only, so NUMA mempolicy is used.
    >
    > task_struct is always allocated from slab.

    Hmm, I meant stack (the thing that might be trashed a lot in ksoftirqd),
    so it is included in struct thread_info

    And this one uses __get_free_pages(GFP_KERNEL, THREAD_SIZE_ORDER) from
    alloc_thread_info()


    By the way, I re-tested my original patch (MPOL_BIND) on x86_32

    # cat /proc/buddyinfo
    Node 0, zone DMA 0 1 0 1 2 1 1 0 1 1 3
    Node 0, zone Normal 22 14 10 3 2 3 4 2 3 2 165
    Node 0, zone HighMem 41 35 346 223 124 140 40 19 2 0 143
    Node 1, zone HighMem 21 7 8 4 217 97 33 11 3 1 415

    And got correct stacks. Are you sure we must use PREFERRED ?



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