On Tue, 2015-02-10 at 11:33 +0100, Michal Kazior wrote:
> + if (msdu->sk) {
> + ewma_add(&ar->tx_delay_us,
> + ktime_to_ns(ktime_sub(ktime_get(), skb_cb->stamp)) /
> + NSEC_PER_USEC);
> +
> + ACCESS_ONCE(msdu->sk->sk_tx_completion_delay_cushion) =
> + (ewma_read(&ar->tx_delay_us) *
> + msdu->sk->sk_pacing_rate) >> 20;
> + }
> +
Hi Michal
This is almost it ;)
As I said you must do this using u64 arithmetics, we still support 32bit
kernels.
Also, >> 20 instead of / 1000000 introduces a 5% error, I would use a
plain divide, as the compiler will use a reciprocal divide (ie : a
multiply)
We use >> 10 instead of /1000 because a 2.4 % error is probably okay.
ewma_add(&ar->tx_delay_us,
ktime_to_ns(ktime_sub(ktime_get(),
skb_cb->stamp)) /
NSEC_PER_USEC);
u64 val = (u64)ewma_read(&ar->tx_delay_us) *
msdu->sk->sk_pacing_rate;
do_div(val, USEC_PER_SEC);
ACCESS_ONCE(msdu->sk->sk_tx_completion_delay_cushion) =
(u32)val;
(WRITE_ONCE() would be better for new kernels, but ACCESS_ONCE() is ok
since we probably want to backport to stable kernels)
Thanks
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