Thread (1 message) 1 message, 1 author, 2007-09-29

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.
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