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=-2.3 required=3.0 tests=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 4A15FC46469 for ; Wed, 12 Sep 2018 06:23:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E3DE520839 for ; Wed, 12 Sep 2018 06:23:23 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E3DE520839 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=guarana.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727365AbeILL0U (ORCPT ); Wed, 12 Sep 2018 07:26:20 -0400 Received: from aws.guarana.org ([13.237.110.252]:48694 "EHLO aws.guarana.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725910AbeILL0U (ORCPT ); Wed, 12 Sep 2018 07:26:20 -0400 X-Greylist: delayed 526 seconds by postgrey-1.27 at vger.kernel.org; Wed, 12 Sep 2018 07:26:19 EDT Received: by aws.guarana.org (Postfix, from userid 1006) id 76624A1454; Wed, 12 Sep 2018 06:14:33 +0000 (UTC) Date: Wed, 12 Sep 2018 06:14:33 +0000 From: Kevin Easton To: "Jason A. Donenfeld" Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net, gregkh@linuxfoundation.org, Andy Lutomirski , Thomas Gleixner , Samuel Neves , linux-arch@vger.kernel.org Subject: Re: [PATCH net-next v3 01/17] asm: simd context helper API Message-ID: <20180912061433.GA8484@ip-172-31-15-78> References: <20180911010838.8818-1-Jason@zx2c4.com> <20180911010838.8818-2-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180911010838.8818-2-Jason@zx2c4.com> 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 Mon, Sep 10, 2018 at 07:08:21PM -0600, Jason A. Donenfeld wrote: > Sometimes it's useful to amortize calls to XSAVE/XRSTOR and the related > FPU/SIMD functions over a number of calls, because FPU restoration is > quite expensive. This adds a simple header for carrying out this pattern: > > simd_context_t simd_context = simd_get(); > while ((item = get_item_from_queue()) != NULL) { > encrypt_item(item, simd_context); > simd_context = simd_relax(simd_context); > } > simd_put(simd_context); > > The relaxation step ensures that we don't trample over preemption, and > the get/put API should be a familiar paradigm in the kernel. Given that it's always supposed to be used like that, mightn't it be better if simd_relax() took a pointer to the context, so the call is just simd_relax(&simd_context); ? The inlining means that there won't actually be a pointer dereference in the emitted code. If simd_put() also took a pointer then it could set the context back to HAVE_NO_SIMD as well? - Kevin