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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 0B869C432C0 for ; Mon, 2 Dec 2019 13:51:19 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CE5F3206F0 for ; Mon, 2 Dec 2019 13:51:18 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="sBDFLU0c" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CE5F3206F0 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender:Content-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=K9q7W472QGPapGRvZdH5ciwqvxNFFKt2h4ytYvX2YC0=; b=sBDFLU0cIFS6SuPaK/Izu16Rz EDQMRaMfNT3HH+a7bPdWov74zHU1mqaa9IlVzPoI2H7xa2tYXMRxRcDakIXjcZckYloWs7MUQUuDz VMHWa52O1Ou4DI98CWDsqyEolrweSuv50PwcNxXCWbT/5N0szQ6ED7X8wUTmdpi5a+chFV06yM6MP eqhv8zIL0af3En22EgqguBCRBI208pGpb79EKgAx8wqkpAqU6/XhZ4oM3C7UsXHXVShBPFa0ULT15 xyX8AyQPMzkkaOdW6ctHaSn6lcDdcek6mr5l2hp5UckfOiFzSZCWxFu8DTifUghYtf7Usn2vlXuxm Bnc+wUgJA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ibm6g-0001lA-9Q; Mon, 02 Dec 2019 13:51:18 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1ibm6c-0001kM-Gd for linux-arm-kernel@lists.infradead.org; Mon, 02 Dec 2019 13:51:16 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CED6130E; Mon, 2 Dec 2019 05:51:10 -0800 (PST) Received: from [10.1.196.37] (e121345-lin.cambridge.arm.com [10.1.196.37]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 598313F68E; Mon, 2 Dec 2019 05:51:09 -0800 (PST) Subject: Re: [PATCH v1] clk: Convert managed get functions to devm_add_action API To: Marc Gonzalez , Dmitry Torokhov , Bjorn Andersson References: <3d8a58bf-0814-1ec1-038a-10a20b9646ad@free.fr> <20191128185630.GK82109@yoga> <20191202014237.GR248138@dtor-ws> From: Robin Murphy Message-ID: Date: Mon, 2 Dec 2019 13:51:08 +0000 User-Agent: Mozilla/5.0 (X11; Linux aarch64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191202_055114_636438_26F598CB X-CRM114-Status: GOOD ( 21.10 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Kuninori Morimoto , Stephen Boyd , Michael Turquette , LKML , linux-clk , Russell King , Linux ARM , Sudip Mukherjee , Guenter Roeck Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 02/12/2019 9:25 am, Marc Gonzalez wrote: > On 02/12/2019 02:42, Dmitry Torokhov wrote: > >> On Thu, Nov 28, 2019 at 10:56:30AM -0800, Bjorn Andersson wrote: >> >>> On Tue 26 Nov 08:13 PST 2019, Marc Gonzalez wrote: >>> >>>> Date: Tue, 26 Nov 2019 13:56:53 +0100 >>>> >>>> Using devm_add_action_or_reset() produces simpler code and smaller >>>> object size: >>>> >>>> 1 file changed, 16 insertions(+), 46 deletions(-) >>>> >>>> text data bss dec hex filename >>>> - 1797 80 0 1877 755 drivers/clk/clk-devres.o >>>> + 1499 56 0 1555 613 drivers/clk/clk-devres.o >>>> >>>> Signed-off-by: Marc Gonzalez >>> >>> Looks neat >>> >>> Reviewed-by: Bjorn Andersson >> >> This however increases the runtime costs as each custom action cost us >> an extra pointer. Given that in a system we likely have many clocks >> managed by devres, I am not sure that this code savings is actually >> gives us overall win. It might still, I just want to understand how we >> are allocating/packing devres structures. > > I'm not 100% sure what you are saying. You reduce the text size by a constant amount, at the cost of allocating twice as much runtime data per clock (struct action_devres vs. void*). Assuming 64-bit pointers, that means that in principle your ~320-byte saving would be cancelled out at ~40 managed clocks. However, that's also assuming that the minimum allocation granularity is no larger than a single pointer, which generally isn't true, so in reality it depends on whether the difference in data pushes the total struct devres allocation over the next ARCH_KMALLOC_MINALIGN boundary - if it doesn't, the difference comes entirely for free; if it does, the memory cost tradeoff gets even worse. Robin. > Are you arguing that the proposed patch increases the run-time cost of > devm_clk_put() so much that the listed improvements (simpler source code, > smaller object size) are not worth it? > > AFAIU, the release action is only called > - explicitly, when devm_clk_put() is called > - implicitly, when the device is removed > > How often are clocks removed? > > In hot code-path (called hundreds of times per second) it makes sense to > write more complex code, to shave a few cycles every iteration. But in > cold code-path, I think it's better to write short/simple code. > > Regards. > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel