From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ananyev, Konstantin" Subject: Re: [PATCH v2] mbuf: decrease refcnt when detaching Date: Tue, 17 May 2016 13:44:46 +0000 Message-ID: <2601191342CEEE43887BDE71AB97725836B518CE@irsmsx105.ger.corp.intel.com> References: <1463327436-6863-1-git-send-email-h.mikita89@gmail.com> <2164081.rUYNJaTDcf@xps13> <2601191342CEEE43887BDE71AB97725836B518A4@irsmsx105.ger.corp.intel.com> <1709340.0fJkCxgyM5@xps13> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Cc: "dev@dpdk.org" , Hiroyuki Mikita , "olivier.matz@6wind.com" To: Thomas Monjalon Return-path: Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by dpdk.org (Postfix) with ESMTP id 965426A16 for ; Tue, 17 May 2016 15:44:49 +0200 (CEST) In-Reply-To: <1709340.0fJkCxgyM5@xps13> Content-Language: en-US List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" > -----Original Message----- > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com] > Sent: Tuesday, May 17, 2016 2:40 PM > To: Ananyev, Konstantin > Cc: dev@dpdk.org; Hiroyuki Mikita; olivier.matz@6wind.com > Subject: Re: [dpdk-dev] [PATCH v2] mbuf: decrease refcnt when detaching >=20 > 2016-05-17 12:59, Ananyev, Konstantin: > > > > The rte_pktmbuf_detach() function should decrease refcnt on a direc= t > > > > buffer. > > > > > > As you have noticed, "whenever the indirect buffer is detached, > > > the reference counter on the direct buffer is decremented." > > > So the current behaviour of rte_pktmbuf_detach() is buggy. > > > Why not fix it without renaming? > > > If you consider this behavioral bug is part of the API, we > > > can fix it in a new function unattach and deprecate detach. > > > But Konstantin, why do you want to keep a restore function? > > > What is the need? > > > > I think it might be a useful functionality in some situations: > > some users can attach/detach to external memory buffers (no mbufs) > > and similar functionality is required. >=20 > Attach to external memory buffer (raw buffer) is not currently supported. >=20 > > Let say right now examples/vhost/main.c has its own pktmbuf_detach_zcp(= ) >=20 > You should look at the commit http://dpdk.org/commit/68363d85 > "examples/vhost: remove the non-working zero copy code" >=20 > > which is doing pretty much the same - restore original values, after de= taching > > mbuf from external (virtio) memory buffer. > > Would be good if we'll use a standard API function here. >=20 > You are welcome to implement mbuf attach to raw buffer. > But it is not a requirement for this fix. Hmm, still not sure why we can't keep an existing function? Obviously it wouldn't cost anything and I still think might be useful. Konstantin