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From: David Miller <davem@davemloft.net>
To: inguin@gmx.de
Cc: netdev@vger.kernel.org
Subject: Re: [PATCH] Fix tx transfer padding for full-speed USB
Date: Tue, 24 Apr 2012 00:28:08 -0400 (EDT)	[thread overview]
Message-ID: <20120424.002808.1711965470884592541.davem@davemloft.net> (raw)
In-Reply-To: <1334916021-9124-1-git-send-email-inguin@gmx.de>

From: Ingo van Lil <inguin@gmx.de>
Date: Fri, 20 Apr 2012 12:00:21 +0200

> -	padlen = ((skb->len + 4) % 512) ? 0 : 4;
> +	padlen = ((skb->len + 4) % dev->maxpacket) ? 0 : 4;

This is now an expensive modulus operation, instead of
a cheap mask.

Since you know that dev->maxpacket is always a power of two, tell the
compiler this so it can still optimize the expression by changing this
to "& (dev->maxpacket - 1)" and we'll thus avoid the costly modulus.

  reply	other threads:[~2012-04-24  4:28 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-04-20 10:00 [PATCH] Fix tx transfer padding for full-speed USB Ingo van Lil
2012-04-24  4:28 ` David Miller [this message]
2012-04-24  8:05   ` Ingo van Lil
2012-04-24  8:12     ` David Miller

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