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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 EA9CAC43143 for ; Tue, 2 Oct 2018 14:54:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9A45720666 for ; Tue, 2 Oct 2018 14:54:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=android.com header.i=@android.com header.b="QoittbjD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A45720666 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=android.com 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 S1728530AbeJBVhr (ORCPT ); Tue, 2 Oct 2018 17:37:47 -0400 Received: from mail-pl1-f182.google.com ([209.85.214.182]:39465 "EHLO mail-pl1-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726118AbeJBVhr (ORCPT ); Tue, 2 Oct 2018 17:37:47 -0400 Received: by mail-pl1-f182.google.com with SMTP id w14-v6so1807309plp.6 for ; Tue, 02 Oct 2018 07:54:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=android.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-transfer-encoding:content-language; bh=r8vY+r45ERP3hgnbfsBlOdhRBy9zzbtGvcMP35kZByc=; b=QoittbjDYBiQ1D8tc63N1Qd8GGAyXxPXg5YQB6tUAZQpxjtWhQDLFe/LfTdaW/skoG pa25SdJOBVqz3/FKJrm6MgxAbkwhuQS+SJdUewvL3117ddLeGZhRwUHqb753HWjssDax 5b0qP99rh4Ft2q+rBUcabOvKKF82KUYX8pk54rUUYwqGufmNJgkvumoaWGaj8C9JYjpP E8DXwRDTRfl3K0wK278mAfnzu2qSQE7m1AlZnyOHgQ2L+yH2KD9giYaFxVy5iWr18mlR XvwHt3GC1ji5PG8TQY3RnxQ3Lf6KEKeL4e7XRm/Iyi3KVFbOHhsx3iv8IZ+Xcn1GIRW4 MH9w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=r8vY+r45ERP3hgnbfsBlOdhRBy9zzbtGvcMP35kZByc=; b=DTERbc8PvWDEw+JaBbcs4ZD9z6+kiKPJjQQ3LuRqKjXbmjdWbrlJwvbKe1fX2/9BDl oNICC3fCU41S9YAKo6EDjN+X8djKrmo9muJuwPk4ZebLCPqeEYegaAe5RsE3dKMHloZz L9kOMIGqv+HkRA3jqDUySOIG/Q+ZkB7/m8lFL4us6SpVWjmpflEinD3ztkWwg2BzVZfb viwuXhhRwVHkGpqo3u9QdgjLiMn9QZwRfdMDMeT2n9Td9jRcQWxaKX73CI2mjCmojTPe zb9k1bjoQNyqh3EynelS+6Vpyb+GYFdRdCc8JIFrisC2repytx3Xi0kNRb1I/4q9iPFT XG4w== X-Gm-Message-State: ABuFfog4lF8RsU7AXrTz7uUZRpugeeZgifKgn1RXAkFNEEq6H50jzefm KEAxVpk/rv7JD5arMOz/utHHRw== X-Google-Smtp-Source: ACcGV63Y2+dM5URlmzmFg/b6x4YUxUOQ6iP0gPQq4Do3Ew51xuJ3k0yLPqTvZoiH7C4rD1EAjQEn5Q== X-Received: by 2002:a63:6385:: with SMTP id x127-v6mr14847465pgb.10.1538492039470; Tue, 02 Oct 2018 07:53:59 -0700 (PDT) Received: from nebulus.mtv.corp.google.com ([2620:0:1000:1612:b4fb:6752:f21f:3502]) by smtp.googlemail.com with ESMTPSA id f83-v6sm27348685pfa.109.2018.10.02.07.53.48 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Oct 2018 07:53:58 -0700 (PDT) Subject: Re: RESEND and REBASE arm+arm64+aarch32 vdso rewrite To: Russell King - ARM Linux Cc: John Stultz , lkml , James Morse , Catalin Marinas , Will Deacon , Andy Lutomirski , Dmitry Safonov , Mark Rutland , Laura Abbott , Kees Cook , Ard Biesheuvel , Andy Gross , Kevin Brodsky , Andrew Pinski , Thomas Gleixner , linux-arm-kernel , Jeremy Linton References: <20181001175845.168430-1-salyzyn@android.com> <8c09a380-7bc8-a353-aeb7-6591e6c57f68@android.com> <20181002085041.GV30658@n2100.armlinux.org.uk> From: Mark Salyzyn Message-ID: <7b5611cb-5bd0-d906-7013-31dbe55f8dbb@android.com> Date: Tue, 2 Oct 2018 07:53:46 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181002085041.GV30658@n2100.armlinux.org.uk> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-GB Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/02/2018 01:50 AM, Russell King - ARM Linux wrote: > On Mon, Oct 01, 2018 at 01:44:52PM -0700, Mark Salyzyn wrote: >> Despite the gain of 0.4% for screen-on battery life, where Android has a mix >> of 64 and 32 bit applications, thus still relevant _today_ on 64 bit >> architectures (providing vDSO32 for 32-bit applications). > I don't think the issue is what you think it is. 0.4% gain is > equivalent to almost (but not quite) 1 minute extra for a lifetime of > 4 hours. Is that really noticable, and is it worth the churn from > merging this series? Screen on battery life, all other components of the system active, backlights, touchscreen, sensors etc and it still had a measurable impact on power from the portion that came from the CPU complex. This impact came solely from 32 bit applications left over on the 64-bit platforms that did not formerly have vDSO support. 32-bit applications are not going away even with the advent of 64-bit (sound media framework on Android is 32-bit). Reduction in power is also an increase in performance. The microbenchmarks show ~3-10 fold improvement in the actions of acquiring the time of various sorts for 32-bit applications on 64-bit. A savings in the range of sub-microseconds each time(sic) adds up to 0.4% battery improvement overall. > Given that the gain is so marginal, I can see why people find it > difficult to get excited about this series to spend the time reviewing > it. The reviews were intense over the years IMHO, appeasing several stakeholders and testers. Its that final ACK that has been elusive. I have gotten private emails from ARM many times promising some engineering to look at these waiting patiently without feedback. The changes, as requested in the reviews of the past, turned also into moving most vdso maintenance for all architectures of ARM into lib/vdso with no reduction in microbenchmark performance for the other configurations, at least two additional non-arm architectures look like they could readily switch over to using it as well. This is a major win for maintenance (and was not part of the original set). As a result switching 64-ARM vdso assembler to C is a win for maintenance if upstream'd. Given the Android will need to place these patches in their common tree (not there yet because I have required upstream first, but with limits, 2 years seems a bit long to wait for a project started in ARM, then I was asked to help push it forward), not having them upstream, tested, with many eyes on the code, will be a pity and will result in a possible maintenance burden on up to 13000 phone devices. -- Mark