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    SubjectRe: [-mm patch] i386: enable 4k stacks by default
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    Christoph Hellwig <hch@infradead.org> writes:

    > On Mon, Apr 30, 2007 at 12:26:42PM +0200, Andi Kleen wrote:
    > > Alan Cox <alan@lxorguk.ukuu.org.uk> writes:
    > >
    > > > If this still occurs for some
    > > > combinations then the fix would be 8K + 4K IRQ stack, not just to use 8K
    > > > stack
    > >
    > > Yes i've been thinking for some time doing that would be a good idea.
    >
    > Yes, the non-irqstack case should definitively go away. And 8k
    > kernel stacks isn't that little given how much most 64bit architectures
    > have.

    Actually looking at the code it would need some fixes first:

    /*
    * These should really be __section__(".bss.page_aligned") as well, but
    * gcc's 3.0 and earlier don't handle that correctly.
    */
    static char softirq_stack[NR_CPUS * THREAD_SIZE]
    __attribute__((__aligned__(THREAD_SIZE)));

    static char hardirq_stack[NR_CPUS * THREAD_SIZE]
    __attribute__((__aligned__(THREAD_SIZE)));


    With 8K stacks and NR_CPUS==128 that would be 2MB statically reserved. Yuck.
    Really needs to be dynamically allocated. I'll take a look once the .22
    big merge is done.

    -Andi
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