From mboxrd@z Thu Jan 1 00:00:00 1970 From: "David S. Miller" Date: Tue, 23 Sep 2003 18:51:22 +0000 Subject: Re: NS83820 2.6.0-test5 driver seems unstable on IA64 Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org On Tue, 23 Sep 2003 11:51:04 -0700 Grant Grundler wrote: > Even x86 pays at least a one cycle penalty for every misaligned access. Yes, one cycle, and it's completely lost in the noise when it happens. > In general, open source code has no excuse for using misaligned fields. > It's (mostly) avoidable. TCP/IP headers are the historical exception. It's not the TCP/IP headers intrinsically, it's what they are embedded inside of. For example, if the ethernet driver (as nearly all of our's do which can) optimized for an ethernet header followed by an IP header, guess what? That causes ethernet header followed by appletalk followed by IP to do unaligned accesses. It is an unavoidable axoim in the kernel networking. Unaligned accesses will happen, and they aren't a bug and therefore not worthy of mention in the kernel logs any more than "page was freed" :-)