* Re: [patch 08/17] sky2: avoid divide in receive path
[not found] <200709290542.l8T5gAHW002284@imap1.linux-foundation.org>
@ 2007-09-29 5:51 ` Jeff Garzik
0 siblings, 0 replies; only message in thread
From: Jeff Garzik @ 2007-09-29 5:51 UTC (permalink / raw)
To: akpm, shemminger; +Cc: netdev
akpm@linux-foundation•org wrote:
> From: Stephen Hemminger <shemminger@linux-foundation•org>
>
> Avoid divide (modulus) in receive buffer handling path.
>
> Signed-off-by: Stephen Hemminger <shemminger@linux-foundation•org>
> Signed-off-by: Andrew Morton <akpm@linux-foundation•org>
> ---
>
> drivers/net/sky2.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff -puN drivers/net/sky2.c~sky2-avoid-divide-in-receive-path drivers/net/sky2.c
> --- a/drivers/net/sky2.c~sky2-avoid-divide-in-receive-path
> +++ a/drivers/net/sky2.c
> @@ -2155,7 +2155,8 @@ static struct sk_buff *sky2_receive(stru
> printk(KERN_DEBUG PFX "%s: rx slot %u status 0x%x len %d\n",
> dev->name, sky2->rx_next, status, length);
>
> - sky2->rx_next = (sky2->rx_next + 1) % sky2->rx_pending;
> + if (++sky2->rx_next >= sky2->rx_pending)
> + sky2->rx_next = 0;
it is silly to introduce a branch just for this.
require that the ring size is a power-of-2, and then replace the divide
with a mask.
^ permalink raw reply [flat|nested] only message in thread