Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754061AbdIGHEw (ORCPT ); Thu, 7 Sep 2017 03:04:52 -0400 Received: from mail-wr0-f171.google.com ([209.85.128.171]:32849 "EHLO mail-wr0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753826AbdIGHEu (ORCPT ); Thu, 7 Sep 2017 03:04:50 -0400 X-Google-Smtp-Source: ADKCNb7nShiMTehb/+cWPBqpP0V/7j8YUKnCfXb4duYkPmDIQuvBHcrUiB4x62H2JsCqBOIvLp4/Ww== Date: Thu, 7 Sep 2017 09:04:46 +0200 From: Ingo Molnar To: Andy Lutomirski Cc: Andi Kleen , X86 ML , "linux-kernel@vger.kernel.org" , Borislav Petkov , Brian Gerst , Andrew Cooper , Juergen Gross , Boris Ostrovsky , Kees Cook Subject: Re: [RFC 00/17] Pile o' entry stack changes Message-ID: <20170907070446.uu2tzul45r76kj3o@gmail.com> References: <87vakvpj5b.fsf@firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 901 Lines: 24 * Andy Lutomirski wrote: > On Wed, Sep 6, 2017 at 3:16 PM, Andi Kleen wrote: > > Andy Lutomirski writes: > >> > >> - Lots of people (Linus included) have asked to convert the entry > >> code to pop registers on exit instead of movqing them off the > >> stack. This makes a bunch of progress in that direction. > > > > You should benchmark it on Atoms. Likely it's a regression there > > because they don't have the special PUSH/POP acceleration. > > I'm not entirely sure this is a worthwhile reason. Atom will lose a > few cycles due to POP throughput, but there's a lot less decode > bandwidth needed and we save a cache line or two. I think we can also safely assume that Atom will eventually either join the 21st century or die out - mild Atom micro-costs are not a good reason to complicate the entry code... Thanks, Ingo