From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <olivier.matz@6wind.com>
Received: from mail.droids-corp.org (zoll.droids-corp.org [94.23.50.67])
 by dpdk.org (Postfix) with ESMTP id 8C22A1AEEE
 for <dev@dpdk.org>; Fri,  8 Dec 2017 17:19:52 +0100 (CET)
Received: from lfbn-1-6068-189.w90-110.abo.wanadoo.fr ([90.110.3.189]
 helo=droids-corp.org)
 by mail.droids-corp.org with esmtpsa (TLS1.0:RSA_AES_256_CBC_SHA1:256)
 (Exim 4.84_2) (envelope-from <olivier.matz@6wind.com>)
 id 1eNLTR-0006Tf-IL; Fri, 08 Dec 2017 17:26:06 +0100
Received: by droids-corp.org (sSMTP sendmail emulation);
 Fri, 08 Dec 2017 17:19:42 +0100
Date: Fri, 8 Dec 2017 17:19:42 +0100
From: Olivier MATZ <olivier.matz@6wind.com>
To: Ilya Matveychikov <matvejchikov@gmail.com>
Cc: dev@dpdk.org, "Hanoch Haim (hhaim)" <hhaim@cisco.com>,
 konstantin.ananyev@intel.com
Message-ID: <20171208161941.7bjpif7n5kioax4n@platinum>
References: <20171115091413.27119-1-hhaim@cisco.com>
 <20171208154651.16546-1-olivier.matz@6wind.com>
 <60A7E7E9-91D7-48C0-BE51-D284318FD659@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <60A7E7E9-91D7-48C0-BE51-D284318FD659@gmail.com>
User-Agent: NeoMutt/20170113 (1.7.2)
Subject: Re: [dpdk-dev] [PATCH v4] mbuf: fix mbuf free performance with non
	atomic refcnt
X-BeenThere: dev@dpdk.org
X-Mailman-Version: 2.1.15
Precedence: list
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>
X-List-Received-Date: Fri, 08 Dec 2017 16:19:52 -0000

On Fri, Dec 08, 2017 at 08:04:50PM +0400, Ilya Matveychikov wrote:
> Olivier,
> 
> > On Dec 8, 2017, at 7:46 PM, Olivier Matz <olivier.matz@6wind.com> wrote:
> > 
> 
> > 
> > lib/librte_mbuf/rte_mbuf.h | 23 ++++++++++++++++++-----
> > 1 file changed, 18 insertions(+), 5 deletions(-)
> > 
> > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> > index ce8a05ddf..dd08cb72b 100644
> > --- a/lib/librte_mbuf/rte_mbuf.h
> > +++ b/lib/librte_mbuf/rte_mbuf.h
> > @@ -764,6 +764,13 @@ rte_mbuf_refcnt_set(struct rte_mbuf *m, uint16_t new_value)
> > 	rte_atomic16_set(&m->refcnt_atomic, new_value);
> > }
> > 
> > +/* internal */
> > +static inline uint16_t
> > +__rte_mbuf_refcnt_update(struct rte_mbuf *m, int16_t value)
> > +{
> > +	return (uint16_t)(rte_atomic16_add_return(&m->refcnt_atomic, value));
> 
> What’s the purpose of using direct cast to uint16_t here and in other places?

This is just a code move.

Few years ago, I remember that icc was quite quick to trigger warnings when
doing implicit casts. I don't know it it's still true, but that may be the
reason why this was done like this initially, or not.

I agree we could remove this explicit cast, but I think it should go in
another patch, because there are several of them.

Olivier