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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 10345C433EF for ; Wed, 8 Jun 2022 17:33:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229796AbiFHRdg (ORCPT ); Wed, 8 Jun 2022 13:33:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41430 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232263AbiFHRda (ORCPT ); Wed, 8 Jun 2022 13:33:30 -0400 Received: from mail-pl1-f177.google.com (mail-pl1-f177.google.com [209.85.214.177]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8615D262; Wed, 8 Jun 2022 10:33:29 -0700 (PDT) Received: by mail-pl1-f177.google.com with SMTP id n18so18238043plg.5; Wed, 08 Jun 2022 10:33:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=URIZCp/jWQNLisOjE8f9wYPe1lbI6/tMNbNejKjnaZ4=; b=lzGzqmwl6VU+mZZ7frpQ/BD/+BZh+cPqF9BLBHqMuIfiSIPx5qv8xw8N/8eW6zdPe+ +abix3stO3x1VqcgKEk/KKhc9UyS0xRHR5rl3/9zMwoDn1l9e+PYK3wbqDrEAdVMzGrr DJ+H0YADbxOXrHD98ci4X3I8tTRQssvyKSGEJG1K4AfT2D01poOu1wpZN0YUMACuVWLV So0X2TqDojWxvw+fj7AFWQrYaeNNyMk1ZPdkXAlZVGYUtUMBp3dfPzbaIR7d+ug4G0Cy C5OGtFxXZ15IHH161TfnHcUvgC0OWVG9K7QcW8k4xQe+TuEyTQnHseMvg4AVPAYiKwAp k2PA== X-Gm-Message-State: AOAM530bJezeTtIzOJ75zPyey0DN5LQ9RdnnTzSpBUBVSD9isTfNEYyD ZrXb6RaR1CoJt9uvRg62q+akuEvk+2c= X-Google-Smtp-Source: ABdhPJyg/AK8j680Ym1MLmXvtMNO7idwCDt0mxe0LmDZt+QIharawT9S6BKDFL1MLiFHnWCay3fYlA== X-Received: by 2002:a17:902:7886:b0:167:5c8c:4d3e with SMTP id q6-20020a170902788600b001675c8c4d3emr24496557pll.74.1654709608885; Wed, 08 Jun 2022 10:33:28 -0700 (PDT) Received: from ?IPV6:2620:15c:211:201:1cb7:9e5d:5ca4:2a39? ([2620:15c:211:201:1cb7:9e5d:5ca4:2a39]) by smtp.gmail.com with ESMTPSA id t4-20020a1709027fc400b0015e8d4eb28esm15055558plb.216.2022.06.08.10.33.27 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jun 2022 10:33:28 -0700 (PDT) Message-ID: Date: Wed, 8 Jun 2022 10:33:26 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH v3 3/4] scsi: core: Cap shost max_sectors according to DMA optimum mapping limits Content-Language: en-US To: John Garry , damien.lemoal@opensource.wdc.com, joro@8bytes.org, will@kernel.org, jejb@linux.ibm.com, martin.petersen@oracle.com, hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-ide@vger.kernel.org, iommu@lists.linux-foundation.org, linux-scsi@vger.kernel.org, liyihang6@hisilicon.com, chenxiang66@hisilicon.com, thunder.leizhen@huawei.com References: <1654507822-168026-1-git-send-email-john.garry@huawei.com> <1654507822-168026-4-git-send-email-john.garry@huawei.com> From: Bart Van Assche In-Reply-To: <1654507822-168026-4-git-send-email-john.garry@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 6/6/22 02:30, John Garry wrote: > + if (dma_dev->dma_mask) { > + shost->max_sectors = min_t(unsigned int, shost->max_sectors, > + dma_opt_mapping_size(dma_dev) >> SECTOR_SHIFT); > + } Since IOVA_RANGE_CACHE_MAX_SIZE = 6 this limits max_sectors to 2**6 * PAGE_SIZE or 256 KiB if the page size is 4 KiB. I think that's too small. Some (SRP) storage arrays require much larger transfers to achieve optimal performance. Thanks, Bart.