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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 EEFBDC6369E for ; Thu, 19 Nov 2020 14:46:40 +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 7921822261 for ; Thu, 19 Nov 2020 14:46:39 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7921822261 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from bilbo.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 4CcMvJ5CSjzDqpM for ; Fri, 20 Nov 2020 01:46:36 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=csgroup.eu (client-ip=93.17.236.30; helo=pegase1.c-s.fr; envelope-from=christophe.leroy@csgroup.eu; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=csgroup.eu Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4CcMrG6fpgzDqfD for ; Fri, 20 Nov 2020 01:43:49 +1100 (AEDT) Received: from localhost (mailhub1-int [192.168.12.234]) by localhost (Postfix) with ESMTP id 4CcMqy57v7z9v4Wj; Thu, 19 Nov 2020 15:43:42 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [192.168.12.234]) (amavisd-new, port 10024) with ESMTP id 3JMG2h16lAjA; Thu, 19 Nov 2020 15:43:42 +0100 (CET) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4CcMqy22Vsz9v4Wh; Thu, 19 Nov 2020 15:43:42 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id DC4B48B78A; Thu, 19 Nov 2020 15:43:43 +0100 (CET) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id 7u0m1dLxfBpG; Thu, 19 Nov 2020 15:43:43 +0100 (CET) Received: from [192.168.4.90] (unknown [192.168.4.90]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 53F2E8B80B; Thu, 19 Nov 2020 15:43:43 +0100 (CET) Subject: Re: CONFIG_PPC_VAS depends on 64k pages...? To: Will Springer , linuxppc-dev@lists.ozlabs.org, Sukadev Bhattiprolu References: <7171078.EvYhyI6sBW@sheen> From: Christophe Leroy Message-ID: <2b234a7e-e9f6-d02b-a20f-74c0cc1df8d3@csgroup.eu> Date: Thu, 19 Nov 2020 15:43:39 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.3 MIME-Version: 1.0 In-Reply-To: <7171078.EvYhyI6sBW@sheen> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: fr Content-Transfer-Encoding: 8bit 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: daniel@octaforge.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Hi, Le 19/11/2020 à 11:58, Will Springer a écrit : > I learned about the POWER9 gzip accelerator a few months ago when the > support hit upstream Linux 5.8. However, for some reason the Kconfig > dictates that VAS depends on a 64k page size, which is problematic as I > run Void Linux, which uses a 4k-page kernel. > > Some early poking by others indicated there wasn't an obvious page size > dependency in the code, and suggested I try modifying the config to switch > it on. I did so, but was stopped by a minor complaint of an "unexpected DT > configuration" by the VAS code. I wasn't equipped to figure out exactly what > this meant, even after finding the offending condition, so after writing a > very drawn-out forum post asking for help, I dropped the subject. > > Fast forward to today, when I was reminded of the whole thing again, and > decided to debug a bit further. Apparently the VAS platform device > (derived from the DT node) has 5 resources on my 4k kernel, instead of 4 > (which evidently works for others who have had success on 64k kernels). I > have no idea what this means in practice (I don't know how to introspect > it), but after making a tiny patch[1], everything came up smoothly and I > was doing blazing-fast gzip (de)compression in no time. > > Everything seems to work fine on 4k pages. So, what's up? Are there > pitfalls lurking around that I've yet to stumble over? More reasonably, > I'm curious as to why the feature supposedly depends on 64k pages, or if > there's anything else I should be concerned about. > Maybe ask Sukadev who did the implementation and is maintaining it ? > I do have to say I'm quite satisfied with the results of the NX > accelerator, though. Being able to shuffle data to a RaptorCS box over gigE > and get compressed data back faster than most software gzip could ever > hope to achieve is no small feat, let alone the instantaneous results locally. > :) > > Cheers, > Will Springer [she/her] > > [1]: https://github.com/Skirmisher/void-packages/blob/vas-4k-pages/srcpkgs/linux5.9/patches/ppc-vas-on-4k.patch > Christophe