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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 C9CE4C43331 for ; Mon, 11 Nov 2019 13:27:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8ECF9222BD for ; Mon, 11 Nov 2019 13:27:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573478844; bh=3khfY817g3PS5TkES+rklqgKgMSJFdurf0htRIWV3E8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=KXhbXw1HoJI4gtXC8NnZbtm+04+V8TwOA9pPSNo6RCNm4MnhD4ddLiEAbjd3YEssT 2PrIbKhCgNU2xm0U/vqhIwZ8HfNeaBrY2GkLrUT3/lG1g9GNS83kR5E3mXAWPs4IJ/ mrFxa18lw0L5M3P2Ez5B6bvGqPoxjPp1k/5JorP4= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726951AbfKKN1X (ORCPT ); Mon, 11 Nov 2019 08:27:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:40442 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726879AbfKKN1X (ORCPT ); Mon, 11 Nov 2019 08:27:23 -0500 Received: from willie-the-truck (236.31.169.217.in-addr.arpa [217.169.31.236]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id DBCC32196E; Mon, 11 Nov 2019 13:27:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1573478842; bh=3khfY817g3PS5TkES+rklqgKgMSJFdurf0htRIWV3E8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=m+qMg8uHBw99MxUsk26njdjGjDT/Ta8ES+ZVEG2GQ0udk7tYSiKb+Jd1xciKXpB8F twU/HuO8oIndjNsYOzuMjoEa907GWnUixaMXCV1d3Wa3GFZc5BFH+gfgMfWCP1lcli Fpo2XworndBJncJiA4o6dYYhc2YNDoBJat65lfPM= Date: Mon, 11 Nov 2019 13:27:17 +0000 From: Will Deacon To: Zhenyu Ye Cc: catalin.marinas@arm.com, maz@kernel.org, suzuki.poulose@arm.com, mark.rutland@arm.com, tangnianyao@huawei.com, xiexiangyou@huawei.com, linux-kernel@vger.kernel.org, arm@kernel.org Subject: Re: [RFC PATCH v2] arm64: cpufeatures: add support for tlbi range instructions Message-ID: <20191111132716.GA9394@willie-the-truck> References: <5DC960EB.9050503@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5DC960EB.9050503@huawei.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, Nov 11, 2019 at 09:23:55PM +0800, Zhenyu Ye wrote: > ARMv8.4-TLBI provides TLBI invalidation instruction that apply to a > range of input addresses. This patch adds support for this feature. > This is the second version of the patch. > > I traced the __flush_tlb_range() for a minute and get some statistical > data as below: > > PAGENUM COUNT > 1 34944 > 2 5683 > 3 1343 > 4 7857 > 5 838 > 9 339 > 16 933 > 19 427 > 20 5821 > 23 279 > 41 338 > 141 279 > 512 428 > 1668 120 > 2038 100 > > Those data are based on kernel-5.4.0, where PAGENUM = end - start, COUNT > shows number of calls to the __flush_tlb_range() in a minute. There only > shows the data which COUNT >= 100. The kernel is started normally, and > transparent hugepage is opened. As we can see, though most user TLBI > ranges were 1 pages long, the num of long-range can not be ignored. > > The new feature of TLB range can improve lots of performance compared to > the current implementation. As an example, flush 512 ranges needs only 1 > instruction as opposed to 512 instructions using current implementation. > > And for a new hardware feature, support is better than not. > > Signed-off-by: Zhenyu Ye > --- > ChangeLog v1 -> v2: > - Change the main implementation of this feature. > - Add some comments. How does this address my concerns here: https://lore.kernel.org/linux-arm-kernel/20191031131649.GB27196@willie-the-truck/ ? Will