From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <dev-bounces@dpdk.org>
Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124])
	by inbox.dpdk.org (Postfix) with ESMTP id 24DECA00C4;
	Fri,  1 Jul 2022 14:24:43 +0200 (CEST)
Received: from [217.70.189.124] (localhost [127.0.0.1])
	by mails.dpdk.org (Postfix) with ESMTP id BF2734069D;
	Fri,  1 Jul 2022 14:24:42 +0200 (CEST)
Received: from mx0b-0016f401.pphosted.com (mx0a-0016f401.pphosted.com
 [67.231.148.174])
 by mails.dpdk.org (Postfix) with ESMTP id B7E6940150
 for <dev@dpdk.org>; Fri,  1 Jul 2022 14:24:40 +0200 (CEST)
Received: from pps.filterd (m0045849.ppops.net [127.0.0.1])
 by mx0a-0016f401.pphosted.com (8.17.1.5/8.17.1.5) with ESMTP id 2611krjg012686;
 Fri, 1 Jul 2022 05:24:39 -0700
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=marvell.com;
 h=from : to : cc :
 subject : date : message-id : in-reply-to : references : mime-version :
 content-transfer-encoding : content-type; s=pfpt0220;
 bh=I33U+ly91BltLO0ijzpBlstukm8meL8w/vdPI64qT6I=;
 b=B+vY0MPUaykuV87i92Ejur+tIvian6Ziu/pOoxCht2ibOD1Ui3I4CGicEVjr09JyRwkh
 836a9gkL6bNpA5ov6Ueg68ipi+WUFd0SW3J3Ur3kST9lSVSQVy5Xnkjk7re7PbjI7myw
 mUPzqng25L0/o5KqSWW+5X9A8Oj2E+eh5dI1yugse1OTws6A7xDFs134K4UiTdOqm5Vm
 IlXGZOpPiQN1MbCZqsq66drx04hx5ds6u7DXyZKdqPiUGqTaLMoPeBcPN4P/QMt9CYao
 Y7517yDkh2PHEqDvnCjgmQ2Li1gGQGjVJmWC8i6tMuTIUl0wK5T7AQPKJXSnIn1I/wLN cw== 
Received: from dc5-exch01.marvell.com ([199.233.59.181])
 by mx0a-0016f401.pphosted.com (PPS) with ESMTPS id 3h1akbncvg-1
 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT);
 Fri, 01 Jul 2022 05:24:38 -0700
Received: from DC5-EXCH02.marvell.com (10.69.176.39) by DC5-EXCH01.marvell.com
 (10.69.176.38) with Microsoft SMTP Server (TLS) id 15.0.1497.2;
 Fri, 1 Jul 2022 05:24:37 -0700
Received: from maili.marvell.com (10.69.176.80) by DC5-EXCH02.marvell.com
 (10.69.176.39) with Microsoft SMTP Server id 15.0.1497.18 via Frontend
 Transport; Fri, 1 Jul 2022 05:24:37 -0700
Received: from localhost.localdomain (unknown [10.28.34.29])
 by maili.marvell.com (Postfix) with ESMTP id 5796C3F7041;
 Fri,  1 Jul 2022 05:24:35 -0700 (PDT)
From: Shijith Thotton <sthotton@marvell.com>
To: <stephen@networkplumber.org>
CC: <dev@dpdk.org>, <jerinj@marvell.com>, <olivier.matz@6wind.com>,
 <sthotton@marvell.com>, <thomas@monjalon.net>
Subject: Re: [PATCH] mbuf: add mbuf physical address field to dynamic field
Date: Fri, 1 Jul 2022 17:54:34 +0530
Message-ID: <20220701122434.1887783-1-sthotton@marvell.com>
X-Mailer: git-send-email 2.25.1
In-Reply-To: <20220630094538.5b27d0c6@hermes.local>
References: <20220630094538.5b27d0c6@hermes.local>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Content-Type: text/plain
X-Proofpoint-GUID: 63yCZcsGhDj0n7bRLo67XNCIxnfgc-Bg
X-Proofpoint-ORIG-GUID: 63yCZcsGhDj0n7bRLo67XNCIxnfgc-Bg
X-Proofpoint-Virus-Version: vendor=baseguard
 engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1
 definitions=2022-07-01_07,2022-06-28_01,2022-06-22_01
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <https://mails.dpdk.org/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://mails.dpdk.org/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <https://mails.dpdk.org/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org

>> If all devices are configured to run in IOVA mode as VA, physical
>> address field of mbuf (buf_iova) won't be used. In such cases, buf_iova
>> space is free to use as a dynamic field. So a new dynamic field member
>> (dynfield2) is added in mbuf structure to make use of that space.
>>
>> A new mbuf flag RTE_MBUF_F_DYNFIELD2 is introduced to help identify the
>> mbuf that can use dynfield2.
>>
>> Signed-off-by: Shijith Thotton <sthotton@marvell.com>
>
> This seems like a complex and potentially error prone way to do this.
> What is the use case?
>

PCI drivers with the flag RTE_PCI_DRV_NEED_IOVA_AS_VA only works in IOVA mode as
VA. buf_iova field of mbuf is not used by those PMDs and can be used as a
dynamic area to save space.

> How much of a performance gain?

No change in performance.