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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 81695C31E5B for ; Mon, 17 Jun 2019 23:52:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5B226208C0 for ; Mon, 17 Jun 2019 23:52:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727443AbfFQXw3 (ORCPT ); Mon, 17 Jun 2019 19:52:29 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:46512 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726427AbfFQXw3 (ORCPT ); Mon, 17 Jun 2019 19:52:29 -0400 Received: by mail-pg1-f196.google.com with SMTP id v9so6600957pgr.13; Mon, 17 Jun 2019 16:52:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=rT1Ry9CXDU/Gof/gNESKymfMi9a8wIc43QBygQM/oWk=; b=mJ8Jlyf5c5CQr32tFtn4QQKxZrgQtMFLlzgKU1/UcwURQq2ZCFE1OGJtEtb3WAV3Tk ZNlvZ8SOnjROFsW0jpfyIrzcr4T3FYEds3Rt9DsWO03Nrg9hfEMQgoArhGc6beUsxsxf Jc/qlKMvXm9QK1r+IHwTE2rumUeI71Gx9WvW+IdZturb9TrmX9S3mwPFUb1tfkSm0sso geYJpvOXgTXgmXcG+gGg3FNEvYgJaKV4gAt144FB1C+7lAhOh7so1ZM8nrgI4dZTrgT9 Np3epluPIoVTGX9eJmW7p5kUsGVLO7OTleZj4rBlhLikyV3whn3gZv2zG7nK0L/6QnQw pu8Q== X-Gm-Message-State: APjAAAVUBRH8HZSxjZCPsHsddXOdjqTpXuEfWgJbA5pCQPmLBZNNDgKu ffAvLtnIIgormnADur5a5ps= X-Google-Smtp-Source: APXvYqznUwe7i1jFQEHoTI8nFDF4yUuM+GrXTOznm/OWpDdnoDTWVknSAtGeEiPT6OHomWHWWX0woA== X-Received: by 2002:a17:90a:2ec2:: with SMTP id h2mr1867192pjs.119.1560815548541; Mon, 17 Jun 2019 16:52:28 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id l20sm11750101pff.102.2019.06.17.16.52.26 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 17 Jun 2019 16:52:27 -0700 (PDT) Subject: Re: [PATCH V4 00/16] use sg helper to operate scatterlist To: Ming Lei , linux-scsi@vger.kernel.org, "Martin K . Petersen" Cc: James Bottomley , Hannes Reinecke , Christoph Hellwig , Jim Gill , Cathy Avery , "Ewan D . Milne" , Brian King , James Smart , "Juergen E . Fischer" , Michael Schmitz , Finn Thain , Greg Kroah-Hartman , devel@driverdev.osuosl.org, linux-usb@vger.kernel.org, Dan Carpenter , Benjamin Block References: <20190617030349.26415-1-ming.lei@redhat.com> From: Bart Van Assche Message-ID: <25be959c-82fc-996e-76ed-c1fe7b4dce5d@acm.org> Date: Mon, 17 Jun 2019 16:52:25 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190617030349.26415-1-ming.lei@redhat.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On 6/16/19 8:03 PM, Ming Lei wrote: > Scsi MQ makes a large static allocation for the first scatter gather > list chunk for the driver to use. This is a performance headache we'd > like to fix by reducing the size of the allocation to a 2 element > array. Doing this will break the current guarantee that any driver > using SG_ALL doesn't need to use the scatterlist iterators and can get > away with directly dereferencing the array. Thus we need to update all > drivers to use the scatterlist iterators and remove direct indexing of > the scatterlist array before reducing the initial scatterlist > allocation size in SCSI. For all patches in this series except 9/16 and 11/16, please add the following: Reviewed-by: Bart Van Assche