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=-4.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 4630CC282CE for ; Tue, 4 Jun 2019 13:05:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 19F7323A79 for ; Tue, 4 Jun 2019 13:05:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="VQl8HXs1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727229AbfFDNFj (ORCPT ); Tue, 4 Jun 2019 09:05:39 -0400 Received: from mail-lj1-f195.google.com ([209.85.208.195]:42704 "EHLO mail-lj1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727093AbfFDNFi (ORCPT ); Tue, 4 Jun 2019 09:05:38 -0400 Received: by mail-lj1-f195.google.com with SMTP id t28so8479141lje.9; Tue, 04 Jun 2019 06:05:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=AtISXc3jFgJoLSHh5PWT1AZKuf7dNq1h2+HU+Zatn7w=; b=VQl8HXs1JvXKlRqQOH9bH729BCGyptIFjlxS+jppf2VLBZo+mL1enMs5UmCOFlyv3Z 4yJDQT2HFDx/yrQXMuVS1l1J5S4mEJC5pDv7GkyKaa6etpNNGQhY9iewWE/PYdFaVt6U dZIJh3EFXEXFs/i0A4+avgzW97bzdABWVg8VF6YR6CvLRhkbmMJ097ZSHVVEjjYmLH0D rFivNev2y3Gv8KOP82JmOSdewgrhE4DoIalHbgPtzusxZkkUk4imEHOmVmCQaCDAKdFC XpnpCKce7q6C8Z7azvoDK9Tuc6t/QvDp7xZLNen/7xVV5quPsigoJLQqEy5Evls0JDDU M39w== 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-language :content-transfer-encoding; bh=AtISXc3jFgJoLSHh5PWT1AZKuf7dNq1h2+HU+Zatn7w=; b=i/TtvCVwkinWco/tpHszJR2kc5akoNTQlbfdF98nSES1jPL4GPMMImi6TRfRCV+gXo C3Y0OYoFoZeX2Aj6TCoiGFO6+8kgdH0/XzfI+c25cHCXuJ8n6uJYIsVVgTabXBUphk7+ 0vLIdm1U1STb2I/k85lVetmezDE6oDYL2vNtu6dk/nnNePgTZDt2USxTQi/OhmcO/dqw bEIDc9jW6tbVHrukdhBvF32khoZydcT8zp/kIgKWtOCupxjt0072Lh/wbtxHPsP+YQtI q1SZvjqiFEz8ENkAgEu/3g7xKRtNb6ppo3p3HLOtv3yUsOgRZB4ibBPzN9LjoWgD+2hK BPBQ== X-Gm-Message-State: APjAAAXUdvhQ+dYdxvdljpM3uxoj1w59rL3AXY89HoMmGSLUe/GxkqpV Axb4+BV0GgdrD+KHjW1qBG2waBK7 X-Google-Smtp-Source: APXvYqzN2rPb0j0exDHrTMAjnJbEwSNFphqt3mgRuA0QVXlgI5G9vdQFmdEim7ot3iAS1BFrMVcT3g== X-Received: by 2002:a2e:3a01:: with SMTP id h1mr4872724lja.132.1559653535252; Tue, 04 Jun 2019 06:05:35 -0700 (PDT) Received: from [192.168.2.145] ([94.29.35.141]) by smtp.googlemail.com with ESMTPSA id l22sm3205565ljb.39.2019.06.04.06.05.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Jun 2019 06:05:33 -0700 (PDT) Subject: Re: [PATCH v4 05/16] PM / devfreq: tegra: Don't set EMC clock rate to maximum on probe To: Thierry Reding Cc: Jonathan Hunter , MyungJoo Ham , Kyungmin Park , Chanwoo Choi , Tomeu Vizoso , linux-pm@vger.kernel.org, linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190501233815.32643-1-digetx@gmail.com> <20190501233815.32643-6-digetx@gmail.com> <20190604110042.GE16519@ulmo> From: Dmitry Osipenko Message-ID: <71f7b41c-b33f-92fa-e0a5-85fefeb57274@gmail.com> Date: Tue, 4 Jun 2019 16:05:31 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190604110042.GE16519@ulmo> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 04.06.2019 14:00, Thierry Reding пишет: > On Thu, May 02, 2019 at 02:38:04AM +0300, Dmitry Osipenko wrote: >> There is no real benefit from doing so, hence let's drop that rate setting >> for consistency. >> >> Reviewed-by: Chanwoo Choi >> Signed-off-by: Dmitry Osipenko >> --- >> drivers/devfreq/tegra-devfreq.c | 2 -- >> 1 file changed, 2 deletions(-) > > Do you have any numbers to tell how long it would take for the EMC rate > to get incremented? My understanding is that ACTMON basically reacts to > system load, so I could imagine that not setting to the maximum > frequency after this is loaded might make the system slow in the short > term. Only after ACTMON has collected enough data to determine that it > needs to clock the EMC higher would system speed resume normal. > > I guess technically this patch doesn't change anything if the system > already boots at the highest EMC frequency anyway, which I think it does > on many (although not all) devices. > > Anyway, you said you've tested this and are satisfied with the > performance, so it can't be that bad: > > Acked-by: Thierry Reding It takes 12ms for ACTMON to react and then about (couple) hundred microseconds to change memory freq. This is a very short period of time that human being can't notice. AFAIK, in practice there are no devices in the wild that boot up with DRAM clocked at lowest rate. Most devices have a video output and thus require significant memory bandwidth at a boot time already. Secondly, higher memory bandwidth is only really needed for a cases like multimedia, in most generic cases CPU is hitting cache and not utilizing DRAM a lot.