Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933108AbbDJNT2 (ORCPT ); Fri, 10 Apr 2015 09:19:28 -0400 Received: from terminus.zytor.com ([198.137.202.10]:41458 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932644AbbDJNT0 (ORCPT ); Fri, 10 Apr 2015 09:19:26 -0400 Message-ID: <5527CD92.1080901@zytor.com> Date: Fri, 10 Apr 2015 06:18:10 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.5.0 MIME-Version: 1.0 To: Denys Vlasenko , Ingo Molnar , "Paul E. McKenney" CC: Linus Torvalds , Jason Low , Peter Zijlstra , Davidlohr Bueso , Tim Chen , Aswin Chandramouleeswaran , LKML , Borislav Petkov , Andy Lutomirski , Brian Gerst , Thomas Gleixner , Peter Zijlstra Subject: Re: [PATCH] x86: Align jump targets to 1 byte boundaries References: <20150409175652.GI6464@linux.vnet.ibm.com> <20150409183926.GM6464@linux.vnet.ibm.com> <20150410090051.GA28549@gmail.com> <20150410091252.GA27630@gmail.com> <20150410092152.GA21332@gmail.com> <20150410111427.GA30477@gmail.com> <20150410112748.GB30477@gmail.com> <20150410120846.GA17101@gmail.com> <5527C700.3030405@redhat.com> In-Reply-To: <5527C700.3030405@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 788 Lines: 23 On 04/10/2015 05:50 AM, Denys Vlasenko wrote: > > However, I'm an -Os guy. Expect -O2 people to disagree :) > The problem with -Os is that the compiler will make *any* tradeoffs to save a byte. It is really designed to squeeze as much code into a fixed-size chunk, e.g. a ROM, as possible. We have asked for an -Okernel mode from the gcc folks forever. It basically would mean "-Os except when really dumb." As far as the 16-byte alignment, my understanding is not that it is related to the I$ but rather is the decoder datum. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/