On Wed, 2009-10-07 at 15:38 +0800, Wu Fengguang wrote:
> +static void bdi_calc_write_bandwidth(struct backing_dev_info *bdi,
> + unsigned long nr_pages,
> + unsigned long time)
> +{
> + unsigned long bw;
> +
> + bw = HZ * nr_pages / (time | 1);
> + bdi->write_bandwidth = (bdi->write_bandwidth * 63 + bw) / 64;
> +}
If you have block times < 1 jiffy this all falls apart quite quickly.
You could perhaps try to use cpu_clock() for ns resolution timestamps if
this is a real issue.
(I could imagine fast arrays with huge throughput causing small sleeps,
resulting in underestimates of their bandwidth)
Also, 63/64 seems rather slow progress.. maybe that's good.
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