From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965308AbcFMIV3 (ORCPT ); Mon, 13 Jun 2016 04:21:29 -0400 Received: from mga09.intel.com ([134.134.136.24]:56162 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964898AbcFMIV1 (ORCPT ); Mon, 13 Jun 2016 04:21:27 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.26,466,1459839600"; d="scan'208";a="986244447" Subject: Re: [PATCH] mmc: core: add auto bkops support To: Shawn Lin References: <1465182439-27963-1-git-send-email-shawn.lin@rock-chips.com> <575E52AC.6000902@intel.com> <8bbb3f13-efb3-e963-e53f-cf2ca796f319@rock-chips.com> Cc: Ulf Hansson , Jaehoon Chung , linux-mmc@vger.kernel.org, linux-kernel@vger.kernel.org, Doug Anderson , linux-rockchip@lists.infradead.org, Alex Lemberg From: Adrian Hunter Organization: Intel Finland Oy, Registered Address: PL 281, 00181 Helsinki, Business Identity Code: 0357606 - 4, Domiciled in Helsinki Message-ID: <575E6C11.8060709@intel.com> Date: Mon, 13 Jun 2016 11:17:21 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <8bbb3f13-efb3-e963-e53f-cf2ca796f319@rock-chips.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 13/06/16 10:48, Shawn Lin wrote: > On 2016/6/13 14:29, Adrian Hunter wrote: >> On 06/06/16 06:07, Shawn Lin wrote: >>> JEDEC eMMC v5.1 introduce an autonomously initiated method >>> for background operations. >>> >>> Host that wants to enable the device to perform background >>> operations during device idle time, should signal the device >>> by setting AUTO_EN in BKOPS_EN field EXT_CSD[163] to 1b. When >>> this bit is set, the device may start or stop background operations >>> whenever it sees fit, without any notification to the host. >>> >>> When AUTO_EN bit is set, the host should keep the device power >>> active. The host may set or clear this bit at any time based on >>> its power constraints or other considerations. >>> >>> Currently the manual bkops is only be used under the async req >>> circumstances and it's a bit complicated to be controlled as the >>> perfect method is that we should do some idle monitor just as rpm >>> and send HPI each time if receiving rd/wr req. But it will impact >>> performance significantly, especially for random iops since the >>> weight of executing HPI against r/w small piece of LBAs is >>> nonnegligible. >>> >>> So we now prefer to select the auto one unconditionally if supported >>> which makes it as simple as possible. It should really good enough >>> for devices to manage its internal policy for bkops rather than the >>> host, which makes us believe that we could achieve the best >>> performance for all the devices implementing auto bkops and the only >>> thing we should do is to disable it when cutting off the power. >> >> Do you know if there is really a requirement to do that? > > Even without bkops enable, no matter for manual or auto one, FTL should > always do bkops like GC internally when needed to guarantee the > performance and balance the wear leveling. What I thought to do is to > make it more explicitly. > > Because then, what >> is the point of power off notification? > > When power off notification is sent, bkops will be stopped > in _mmc_suspend. So I don't undertand your point here? I am trying to understand why we need to do anything for auto bkops. Since AUTO_EN is persistent, we can leave the decision whether to turn it on to whomever provisions the device. Then we just leave it alone.