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=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 A1BC9C43219 for ; Fri, 3 May 2019 15:34:11 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (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 330292075E for ; Fri, 3 May 2019 15:34:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 330292075E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 44wblM5DBpzDqYP for ; Sat, 4 May 2019 01:34:07 +1000 (AEST) Authentication-Results: lists.ozlabs.org; spf=permerror (mailfrom) smtp.mailfrom=kernel.crashing.org (client-ip=63.228.1.57; helo=gate.crashing.org; envelope-from=segher@kernel.crashing.org; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Received: from gate.crashing.org (gate.crashing.org [63.228.1.57]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 44wbjW2QGrzDqSR for ; Sat, 4 May 2019 01:32:31 +1000 (AEST) Received: from gate.crashing.org (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id x43FWKRm027260; Fri, 3 May 2019 10:32:21 -0500 Received: (from segher@localhost) by gate.crashing.org (8.14.1/8.14.1/Submit) id x43FWIGd027257; Fri, 3 May 2019 10:32:18 -0500 X-Authentication-Warning: gate.crashing.org: segher set sender to segher@kernel.crashing.org using -f Date: Fri, 3 May 2019 10:32:17 -0500 From: Segher Boessenkool To: Alexey Kardashevskiy Subject: Re: [PATCH kernel] prom_init: Fetch flatten device tree from the system firmware Message-ID: <20190503153217.GN8599@gate.crashing.org> References: <20190501034221.18437-1-aik@ozlabs.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190501034221.18437-1-aik@ozlabs.ru> User-Agent: Mutt/1.4.2.3i X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linuxppc-dev@lists.ozlabs.org, Suraj Jitindar Singh , David Gibson Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Wed, May 01, 2019 at 01:42:21PM +1000, Alexey Kardashevskiy wrote: > At the moment, on 256CPU + 256 PCI devices guest, it takes the guest > about 8.5sec to fetch the entire device tree via the client interface > as the DT is traversed twice - for strings blob and for struct blob. > Also, "getprop" is quite slow too as SLOF stores properties in a linked > list. Most OF implementations do it that way. An optimisation that can help a lot is to cache the last accessed node / prop. This of course then requires you to invalidate that cache at many places you did not think about :-/ > However, since [1] SLOF builds flattened device tree (FDT) for another > purpose. [2] adds a new "fdt-fetch" client interface for the OS to fetch > the FDT. Since Linux does not do much more with the device tree, this should work great for it. Segher