From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin LaHaise Subject: Re: alignment faults in 3.6 Date: Fri, 12 Oct 2012 11:00:45 -0400 Message-ID: <20121012150045.GH5453@kvack.org> References: <201210120811.43290.arnd@arndb.de> <20121012090321.GA21164@n2100.arm.linux.org.uk> <20121012110750.GE21164@n2100.arm.linux.org.uk> <20121012114443.GG21164@n2100.arm.linux.org.uk> <1350043692.21172.11815.camel@edumazet-glaptop> <20121012142254.GG5453@kvack.org> <1350053300.21172.12319.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Russell King - ARM Linux , =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= , Arnd Bergmann , linux-arm-kernel@lists.infradead.org, David Laight , netdev@vger.kernel.org, Jon Masters To: Eric Dumazet Return-path: Received: from kanga.kvack.org ([205.233.56.17]:53881 "EHLO kanga.kvack.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758028Ab2JLPAq (ORCPT ); Fri, 12 Oct 2012 11:00:46 -0400 Content-Disposition: inline In-Reply-To: <1350053300.21172.12319.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: On Fri, Oct 12, 2012 at 04:48:20PM +0200, Eric Dumazet wrote: > > Somehow, I doubt anyone would be willing to walk through all the noise the > > faults would likely trigger. > > If this can be mapped to an event that can be used by perf tool, that > might be useful ? There are performance counters for the various different types of alignment faults supported by perf. Modern x86 makes the vast majority of unaligned accesses very low overhead -- the only ones that really hurt are those straddling different vm pages, but even those have little cost compared to obsolete microarchitectures (*cough* P4 *cough*). -ben -- "Thought is the essence of where you are now."