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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 8F191C4321A for ; Sat, 29 Jun 2019 00:12:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 671662083B for ; Sat, 29 Jun 2019 00:12:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561767120; bh=am1jMBFVjx9jbK4hG/L3KSrebHrUKWqRVZh7/Voykxs=; h=Subject:To:Cc:References:From:Date:In-Reply-To:List-ID:From; b=wguUxyjYQfaEZZcum+gy2LgcCJFpnFiSsjUhk25LBrOzCQKEKVVRSiqOJxJMW8M0S C4eTcLN2wt3K1NTkD+Y+cJfQ8U0+FeHgW9rddQdjkBYS55iGG7BThM/XBRh9oslM4J eIYU4eVpwwdZvCpRmk07zvWQDfEDUBQnJsMeMKMk= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726702AbfF2AL4 (ORCPT ); Fri, 28 Jun 2019 20:11:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:42958 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbfF2AL4 (ORCPT ); Fri, 28 Jun 2019 20:11:56 -0400 Received: from [192.168.1.112] (c-24-9-64-241.hsd1.co.comcast.net [24.9.64.241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 9BA962083B; Sat, 29 Jun 2019 00:11:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1561767116; bh=am1jMBFVjx9jbK4hG/L3KSrebHrUKWqRVZh7/Voykxs=; h=Subject:To:Cc:References:From:Date:In-Reply-To:From; b=P6+y+DR4UrkcYh1E/qelgtVQEzNZWN+UKHXYidxDm2vaVATxMpimT8In75ileP3vU Eo+SnsdK/KvAl0rK7Bb8POqgrW7e1i4RnSmjGQCtv8RNArPoJ+51dC1d3XV3qL26NX zZrpxl2xCZMnsciLlKSJBL9sqYs87VG+aUTd7jcc= Subject: Re: [PATCH 1/2] usbip: Skip DMA mapping and unmapping for urb at vhci To: Suwan Kim , stern@rowland.harvard.edu, valentina.manea.m@gmail.com, gregkh@linuxfoundation.org Cc: linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org, shuah References: <20190621174553.28862-1-suwan.kim027@gmail.com> <20190621174553.28862-2-suwan.kim027@gmail.com> From: shuah Message-ID: <10a4f10a-d271-9331-b847-bdc06f9fc9cf@kernel.org> Date: Fri, 28 Jun 2019 18:11:54 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.1 MIME-Version: 1.0 In-Reply-To: <20190621174553.28862-2-suwan.kim027@gmail.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Hi Suwan, On 6/21/19 11:45 AM, Suwan Kim wrote: > vhci doesn’t do dma for remote device. Actually, the real dma > operation is done by network card driver. So, vhci doesn’t use and > need dma address of transfer buffer of urb. > > When vhci supports SG, it is useful to use native SG list instead > of mapped SG list because dma mapping fnuction can adjust the > number of SG list that is urb->num_mapped_sgs. > > But hcd provides dma mapping and unmapping function by defualt. Typo "defualt" > Moreover, it causes unnecessary dma mapping and unmapping which > will be done again at the NIC driver and it wastes CPU cycles. > So, implement map_urb_for_dma and unmap_urb_for_dma function for > vhci in order to skip the dma mapping and unmapping procedure. > How did you verify that unnecessary dma map/unmap are happening? How many CPU cycles did you manage to reduce with this change? thanks, -- Shuah