From mboxrd@z Thu Jan  1 00:00:00 1970
From: Tetsuya Mukawa <mukawa-AlSX/UN32fvPDbFq/vQRIQ@public.gmane.org>
Subject: Re: some questions about  rte_memcpy
Date: Thu, 22 Jan 2015 19:23:49 +0900
Message-ID: <54C0CFB5.909@igel.co.jp>
References: <54C070DF.1050006@huawei.com>
 <20150122044531.GA13230@mhcomputing.net> <54C08B54.50700@huawei.com>
 <20150122073526.GA14800@mhcomputing.net>
Mime-Version: 1.0
Content-Type: text/plain; charset=windows-1252
Content-Transfer-Encoding: quoted-printable
Cc: "dev-VfR2kkLFssw@public.gmane.org" <dev-VfR2kkLFssw@public.gmane.org>
To: Linhaifeng <haifeng.lin-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Return-path: <dev-bounces-VfR2kkLFssw@public.gmane.org>
In-Reply-To: <20150122073526.GA14800-Hv3ogNYU3JfZZajBQzqCxQ@public.gmane.org>
List-Id: patches and discussions about DPDK <dev.dpdk.org>
List-Unsubscribe: <http://dpdk.org/ml/options/dev>,
 <mailto:dev-request-VfR2kkLFssw@public.gmane.org?subject=unsubscribe>
List-Archive: <http://dpdk.org/ml/archives/dev/>
List-Post: <mailto:dev-VfR2kkLFssw@public.gmane.org>
List-Help: <mailto:dev-request-VfR2kkLFssw@public.gmane.org?subject=help>
List-Subscribe: <http://dpdk.org/ml/listinfo/dev>,
 <mailto:dev-request-VfR2kkLFssw@public.gmane.org?subject=subscribe>
Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org
Sender: "dev" <dev-bounces-VfR2kkLFssw@public.gmane.org>

On 2015/01/22 16:35, Matthew Hall wrote:
> On Thu, Jan 22, 2015 at 01:32:04PM +0800, Linhaifeng wrote:
>> Do you mean if call rte_memcpy before rte_eal_init() would crash?why?
> No guarantee. But a theory. It might use some things from the EAL init =
to=20
> figure out which version of the accelerated algorithm to use.

This selection is done at compile-time.
And if the size is constant, I guess DPDK assumes memcpy is replaced by
inline __builtin_memcpy.
I haven't checked the performance of builtin memcpy, but probably much
faster.

Tetsuya

> Matthew.