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=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 6813AC4320E for ; Tue, 31 Aug 2021 20:49:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4ED9260ED4 for ; Tue, 31 Aug 2021 20:49:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241231AbhHaUuR (ORCPT ); Tue, 31 Aug 2021 16:50:17 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229916AbhHaUuP (ORCPT ); Tue, 31 Aug 2021 16:50:15 -0400 Received: from mail-qk1-x736.google.com (mail-qk1-x736.google.com [IPv6:2607:f8b0:4864:20::736]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 33282C061575 for ; Tue, 31 Aug 2021 13:49:20 -0700 (PDT) Received: by mail-qk1-x736.google.com with SMTP id c10so721696qko.11 for ; Tue, 31 Aug 2021 13:49:20 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=message-id:subject:from:to:cc:date:in-reply-to:references :user-agent:mime-version:content-transfer-encoding; bh=0XGq0QWFCnzYO26yFWXj5mnRnRTvlRa41ppVOuxHxJw=; b=OPzpmN8iojb71hEsYdQswFgRF9J5uQa4An56DALbmyvZw6zJCR/N8Q6ipsBdsFV2M3 MmPKYVkEgHeOL711NOoxm4vRV0ZpnAmOFR2Zn/5vnLtSM4TBvzoBuQ1dCa+5xCTzcy4T YXtZhbysJ3yFxd4kXf7oCr2LfWoSx5zAJMHS5KbGIPzvCzXf9EeHPa9JSji2fs9CsbKj vp35vzB5nH0/g4LS5we3vACD2iPRT5T2XTqUKvcDP1XTBeWgyzgsaAXT66+CRfmOqiyn fl5hr8udJncyK9g9khAmpIOgwuEUjL1yTA+FfAIv11tQsET/e45BQOr9CwCOtvie93wo +DFw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version:content-transfer-encoding; bh=0XGq0QWFCnzYO26yFWXj5mnRnRTvlRa41ppVOuxHxJw=; b=htwnnEveEFaeS9apdnc45Ztdc+FuHIyJmu3LaJQejKlzmUI0lXN5vXgPt7g7siC3eS 1kgQ5WRs1Z7gXqfSJ4GRGfN+1TFQGFXkxl6kmjSNLM9TPEoZPzn5Do6dVt5hd6jFIJFE cJpRJdgqFeg0QoMwEXHZi03BYbvpaXGRBoRJfoDT7/SFadwoo6u8k4S7reJwR/mVbiP7 1JK3AxG5DZ64noFiURe3TAhEHSbix68rLlY61hq3oS8M6CyZgerHDOpMG0PaIiolLJxJ FJiHsp9I7GMN7Cee9wDIhgYTk07VXhz+Av4ghvZGjkFMU4Y6JsQ3U/SoCArOIQm13PrJ km+w== X-Gm-Message-State: AOAM531nULVi5czo86gsuHV9wTGA0xjZvxDE7atIUh6mpHVewDQiL+AK /QkxPiu0jYkOzIP7dtIrbWy1xweLzQk= X-Google-Smtp-Source: ABdhPJzHNi57SmFcQgygfZZHQNyCxnxCZeGp0wu/IiKtXd+dWkDZkVnEU/lmwwE0ENmjHdWWIDCBDA== X-Received: by 2002:a37:a853:: with SMTP id r80mr4977523qke.326.1630442959347; Tue, 31 Aug 2021 13:49:19 -0700 (PDT) Received: from ?IPv6:2804:431:c7f1:e948:8e69:9cd6:5512:12f4? ([2804:431:c7f1:e948:8e69:9cd6:5512:12f4]) by smtp.gmail.com with ESMTPSA id x27sm5300509qtm.23.2021.08.31.13.49.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 31 Aug 2021 13:49:18 -0700 (PDT) Message-ID: Subject: Re: [PATCH v6 00/11] DDW + Indirect Mapping From: Leonardo =?ISO-8859-1?Q?Br=E1s?= To: David Christensen , Michael Ellerman , Benjamin Herrenschmidt , Paul Mackerras , Alexey Kardashevskiy , David Gibson , kernel test robot , Nicolin Chen , Frederic Barrat Cc: linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org Date: Tue, 31 Aug 2021 17:49:36 -0300 In-Reply-To: <311ece8f-bedc-b3f7-0d1b-2cb78438890f@linux.vnet.ibm.com> References: <20210817063929.38701-1-leobras.c@gmail.com> <82ca56ab-6a0a-7cbb-a5e7-facc40f35c3c@linux.vnet.ibm.com> <311ece8f-bedc-b3f7-0d1b-2cb78438890f@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.40.4 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2021-08-31 at 13:39 -0700, David Christensen wrote: > > > > This series allow Indirect DMA using DDW when available, which > > usually > > means bigger pagesizes and more TCEs, and so more DMA space. > > How is the mapping method selected?  LPAR creation via the HMC, Linux > kernel load parameter, or some other method? At device/bus probe, if there is enough DMA space available for Direct DMA, then it's used. If not, it uses indirect DMA. > > The hcall overhead doesn't seem too worrisome when mapping 1GB pages > so > the Indirect DMA method might be best in my situation (DPDK). Well, it depends on usage. I mean, the recommended use of IOMMU is to map, transmit and then unmap, but this will vary on the implementation of the driver. If, for example, there is some reuse of the DMA mapping, as in a previous patchset I sent (IOMMU Pagecache), then the hcall overhead can be reduced drastically. > > Dave Best regards, Leonardo