Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752493AbdIGABr (ORCPT ); Wed, 6 Sep 2017 20:01:47 -0400 Received: from mail.kernel.org ([198.145.29.99]:59348 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751267AbdIGABp (ORCPT ); Wed, 6 Sep 2017 20:01:45 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 52DDA21EA5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=luto@kernel.org X-Google-Smtp-Source: ADKCNb6Gu8ZobdPhlcSKV6nQzoMEbayrQ1xdHs61lSA93jPIJqt/WIotn5fS9KWn7McQLmbUaa/UaMEr41bULtjg7zk= MIME-Version: 1.0 In-Reply-To: <87vakvpj5b.fsf@firstfloor.org> References: <87vakvpj5b.fsf@firstfloor.org> From: Andy Lutomirski Date: Wed, 6 Sep 2017 17:01:24 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [RFC 00/17] Pile o' entry stack changes To: Andi Kleen Cc: Andy Lutomirski , X86 ML , "linux-kernel@vger.kernel.org" , Borislav Petkov , Brian Gerst , Andrew Cooper , Juergen Gross , Boris Ostrovsky , Kees Cook Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 643 Lines: 15 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. --Andy