Re: [patch 08/17] sky2: avoid divide in receive path
From: Jeff Garzik <hidden>
Date: 2007-09-29 05:51:20
akpm@linux-foundation.org wrote:
quoted hunk
From: Stephen Hemminger <redacted> Avoid divide (modulus) in receive buffer handling path. Signed-off-by: Stephen Hemminger <redacted> 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.