From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AB15C282D7 for ; Wed, 30 Jan 2019 11:36:07 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E088E20844 for ; Wed, 30 Jan 2019 11:36:06 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=alien8.de header.i=@alien8.de header.b="jUcPoSJO" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730747AbfA3LgF (ORCPT ); Wed, 30 Jan 2019 06:36:05 -0500 Received: from mail.skyhub.de ([5.9.137.197]:58802 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727500AbfA3LgE (ORCPT ); Wed, 30 Jan 2019 06:36:04 -0500 Received: from zn.tnic (p200300EC2BCAED00302FA729E39312A6.dip0.t-ipconnect.de [IPv6:2003:ec:2bca:ed00:302f:a729:e393:12a6]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.skyhub.de (SuperMail on ZX Spectrum 128k) with ESMTPSA id 808081EC05C2; Wed, 30 Jan 2019 12:36:03 +0100 (CET) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=alien8.de; s=dkim; t=1548848163; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references; bh=RnbxQeaeiJXykNiMzCEPP3bGDnRDsBKzyrDwGd+xh5I=; b=jUcPoSJOIDzE8QRLd1ibZP31oMUE5jf9/SNbaU8qh0DA5NROUPmQ8vpSyKP//Ec/4x3wSq iNZ3FwiJey8MYME48/ngxpLY1TDNdj+QpkHdjWaLf36eZK9hmKz9igL+pec19cM22Y5MN6 0x4S5Kfr4IQq3uzXA45UxrxU8luzJjI= Date: Wed, 30 Jan 2019 12:35:55 +0100 From: Borislav Petkov To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, x86@kernel.org, Andy Lutomirski , Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , kvm@vger.kernel.org, "Jason A. Donenfeld" , Rik van Riel , Dave Hansen Subject: Re: [PATCH v6] x86: load FPU registers on return to userland Message-ID: <20190130113555.GC18383@zn.tnic> References: <20190109114744.10936-1-bigeasy@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190109114744.10936-1-bigeasy@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 09, 2019 at 12:47:22PM +0100, Sebastian Andrzej Siewior wrote: > This is a refurbished series originally started by by Rik van Riel. The > goal is load the FPU registers on return to userland and not on every > context switch. By this optimisation we can: > - avoid loading the registers if the task stays in kernel and does > not return to userland > - make kernel_fpu_begin() cheaper: it only saves the registers on the > first invocation. The second invocation does not need save them again. Btw, do we have any benchmark data showing the improvement this brings? -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.