From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jiayu Hu <jiayu.hu@intel.com>
Subject: Re: [PATCH v8 2/3] lib/gro: add TCP/IPv4 GRO support
Date: Fri, 30 Jun 2017 10:07:25 +0800
Message-ID: <20170630020725.GA13512@jiayu-Has>
References: <1498459430-116048-1-git-send-email-jiayu.hu@intel.com>
 <1498733940-117800-1-git-send-email-jiayu.hu@intel.com>
 <1498733940-117800-3-git-send-email-jiayu.hu@intel.com>
 <20170629105150.74b8bf88@xeon-e3>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: dev@dpdk.org, konstantin.ananyev@intel.com, jianfeng.tan@intel.com,
 yliu@fridaylinux.org, jingjing.wu@intel.com, tiwei.bie@intel.com,
 lei.a.yao@intel.com
To: Stephen Hemminger <stephen@networkplumber.org>
Return-path: <dev-bounces@dpdk.org>
Received: from mga03.intel.com (mga03.intel.com [134.134.136.65])
 by dpdk.org (Postfix) with ESMTP id 7F5412B84
 for <dev@dpdk.org>; Fri, 30 Jun 2017 04:08:41 +0200 (CEST)
Content-Disposition: inline
In-Reply-To: <20170629105150.74b8bf88@xeon-e3>
List-Id: DPDK patches and discussions <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request@dpdk.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev@dpdk.org>
List-Help: <mailto:dev-request@dpdk.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request@dpdk.org?subject=subscribe>
Errors-To: dev-bounces@dpdk.org
Sender: "dev" <dev-bounces@dpdk.org>

Hi Stephen,

On Thu, Jun 29, 2017 at 10:51:50AM -0700, Stephen Hemminger wrote:
> On Thu, 29 Jun 2017 18:58:59 +0800
> Jiayu Hu <jiayu.hu@intel.com> wrote:
> 
> > +	/* allocate a reassembly table for TCP/IPv4 GRO */
> > +	uint32_t tcp_item_num = RTE_MIN(item_num,
> > +			RTE_GRO_MAX_BURST_ITEM_NUM);
> > +	struct gro_tcp_tbl tcp_tbl;
> > +	struct gro_tcp_key tcp_keys[tcp_item_num];
> > +	struct gro_tcp_item tcp_items[tcp_item_num];
> 
> Variable size structures on stack were not supported by
> CLANG, last time I checked. Why not always max size?

The reason why I try to use the min value is to reduce the
overhead of array initialization. But I ignore the clang issue.
Thanks for your reminder. I will replace it with the max value.

> 
> > +
> > +	struct rte_mbuf *unprocess_pkts[nb_pkts];
> > +	uint16_t unprocess_num = 0;
> > +	int32_t ret;
> > +	uint64_t current_time;
> > +
> > +	if ((param->desired_gro_types & RTE_GRO_TCP_IPV4) == 0)
> > +		return nb_pkts;
> > +
> > +	memset(tcp_keys, 0, sizeof(struct gro_tcp_key) *
> > +			tcp_item_num);
> > +	memset(tcp_items, 0, sizeof(struct gro_tcp_item) *
> > +			tcp_item_num);
> 
> Variable size memset's are slow. They generate 'rep; stoz' last
> I checked in GCC and because of rep instruction it kills multi-execution
> pipeline.

Thanks, I will modify it.

BRs,
Jiayu