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    SubjectRe: [PATCH 06/13] writeback: bdi write bandwidth estimation
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    On Wed, 2010-11-17 at 15:08 -0800, Andrew Morton wrote:
    > On Wed, 17 Nov 2010 12:27:26 +0800
    > Wu Fengguang <fengguang.wu@intel.com> wrote:
    >
    > > + w = min(elapsed / (HZ/100), 128UL);
    >
    > I did try setting HZ=10 many years ago, and the kernel blew up.
    >
    > I do recall hearing of people who set HZ very low, perhaps because
    > their huge machines were seeing performance prolems when the timer tick
    > went off. Probably there's no need to do that any more.
    >
    > But still, we shouldn't hard-wire the (HZ >= 100) assumption if we
    > don't absolutely need to, and I don't think it is absolutely needed
    > here.

    People who do cpu bring-up on very slow FPGAs also lower HZ as far as
    possible.


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