From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com (mga01.intel.com [192.55.52.88]) by dpdk.org (Postfix) with ESMTP id 80A5B5A44 for ; Wed, 18 Feb 2015 11:22:08 +0100 (CET) Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga101.fm.intel.com with ESMTP; 18 Feb 2015 02:22:06 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.09,600,1418112000"; d="scan'208";a="667988169" Received: from irsmsx109.ger.corp.intel.com ([163.33.3.23]) by fmsmga001.fm.intel.com with ESMTP; 18 Feb 2015 02:22:05 -0800 Received: from irsmsx105.ger.corp.intel.com ([169.254.7.117]) by IRSMSX109.ger.corp.intel.com ([169.254.13.103]) with mapi id 14.03.0195.001; Wed, 18 Feb 2015 10:22:05 +0000 From: "Ananyev, Konstantin" To: Olivier MATZ , "Richardson, Bruce" Thread-Topic: [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references Thread-Index: AQHQSgLlubcXB2CIb0Ksk8gcVlJrSpz2I0IAgAAFSACAAAIAoIAABMSAgAAEGACAAACU4A== Date: Wed, 18 Feb 2015 10:22:04 +0000 Message-ID: <2601191342CEEE43887BDE71AB977258213EF624@irsmsx105.ger.corp.intel.com> References: <1424102913-18944-1-git-send-email-sergio.gonzalez.monroy@intel.com> <1424102913-18944-3-git-send-email-sergio.gonzalez.monroy@intel.com> <54E45888.7070603@6wind.com> <20150218093548.GA14884@bricha3-MOBL3> <2601191342CEEE43887BDE71AB977258213EF5E4@irsmsx105.ger.corp.intel.com> <20150218100003.GA14728@bricha3-MOBL3> <54E46612.7050809@6wind.com> In-Reply-To: <54E46612.7050809@6wind.com> Accept-Language: en-IE, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.181] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 18 Feb 2015 10:22:09 -0000 > -----Original Message----- > From: Olivier MATZ [mailto:olivier.matz@6wind.com] > Sent: Wednesday, February 18, 2015 10:15 AM > To: Richardson, Bruce; Ananyev, Konstantin > Cc: dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references >=20 > On 02/18/2015 11:00 AM, Bruce Richardson wrote: > > On Wed, Feb 18, 2015 at 09:48:58AM +0000, Ananyev, Konstantin wrote: > >> Hi lads, > >> > >>> -----Original Message----- > >>> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson > >>> Sent: Wednesday, February 18, 2015 9:36 AM > >>> To: Olivier MATZ > >>> Cc: dev@dpdk.org > >>> Subject: Re: [dpdk-dev] [PATCH 2/2] Remove RTE_MBUF_REFCNT references > >>> > >>> On Wed, Feb 18, 2015 at 10:16:56AM +0100, Olivier MATZ wrote: > >>>> Hi Sergio, > >>>> > >>>> On 02/16/2015 05:08 PM, Sergio Gonzalez Monroy wrote: > >>>>> This patch removes all references to RTE_MBUF_REFCNT, setting the r= efcnt > >>>>> field in the mbuf struct permanently. > >>>>> > >>>>> Signed-off-by: Sergio Gonzalez Monroy > >>>> > >>>> I think removing the refcount compile option goes in the right > >>>> direction. However, activating the refcount will break the applicati= ons > >>>> that reserve a private zone in mbufs. This is due to the macros > >>>> RTE_MBUF_TO_BADDR() and RTE_MBUF_FROM_BADDR() that suppose that > >>>> the beginning of the mbuf is 128 bytes (sizeof mbuf) before the > >>>> data buffer. > >>>> > >>> > >>> While I understand how the macros make certain assumptions, how does = activating > >>> the refcnt specifically lead to the problems you describe? Could you = explain > >>> that part in a bit more detail? > >>> > >>> Thanks, > >>> /Bruce > >>> > >> > >> Olivier, I also don't understand your concern here. > >> As I can see, that patch has nothing to do with RTE_MBUF_FROM_BADDR/ R= TE_MBUF_FROM_BADDR macros. > >> They are still there, for example rte_pktmbuf_detach() still uses it t= o restore mbuf's buf_addr. > >> The only principal change here, is that we don't rely more on RTE_MBU= F_FROM_BADDR to determine, > >> Is that indirect mbuf or not. > >> Instead we use a special falg for that purpose: > >> > >> -#define RTE_MBUF_INDIRECT(mb) (RTE_MBUF_FROM_BADDR((mb)->buf_addr) = !=3D (mb)) > >> +#define RTE_MBUF_INDIRECT(mb) (mb->ol_flags & IND_ATTACHED_MBUF) > >> > >> BTW, Sergio as I said before, I think it should be: > >> #define RTE_MBUF_INDIRECT(mb) ((mb)->ol_flags & IND_ATTACHED_MBUF) > >> > >> Konstantin > >> > >> > >>>> For RTE_MBUF_TO_BADDR(), it's relatively easy to replace it. The > >>>> mbuf pool could store the size of the private size like it's done > >>>> for mbp_priv->mbuf_data_room_size. Using rte_mempool_from_obj(m) > >>>> or m->pool, we can retrieve the mbuf pool and this value, then > >>>> compute the buffer address. > > > > Agreed, that makes sense. > > > >>>> > >>>> For RTE_MBUF_FROM_BADDR(), it's more complex. We could ensure that > >>>> a backpointer to the mbuf is always located before the data buffer, > >>>> but it looks difficult to do. > > > > On the other hand, with the proposed refcnt change Sergio proposes, we = no > > longer use this macro in any of the built-in mbuf handling for freeing = mbufs. > > Does this need to be solved at anything other than the application leve= l? >=20 > It's still used in __rte_pktmbuf_prefree_seg() to retrieve the > parent mbuf (direct) from the indirect mbuf beeing freed. >=20 Yes, if the INDIRECT flag is set. Though I still don't understand, what is the problem with these 2 macros wi= th that patch? Why we need to replace it with something? What exactly you think will be broken? Konstantin >=20 >=20 > >>>> > >>>> Another idea would be to add a field in indirect mbufs that stores > >>>> the pointer to the "parent" mbuf. > >>>> > >>>> Regards, > >>>> Olivier > >>>>