From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by dpdk.org (Postfix) with ESMTP id 95E25B48F for ; Wed, 18 Feb 2015 11:00:09 +0100 (CET) Received: from orsmga003.jf.intel.com ([10.7.209.27]) by orsmga101.jf.intel.com with ESMTP; 18 Feb 2015 02:00:08 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.09,600,1418112000"; d="scan'208";a="529152750" Received: from unknown ([10.243.20.37]) by orsmga003.jf.intel.com with SMTP; 18 Feb 2015 01:51:28 -0800 Received: by (sSMTP sendmail emulation); Wed, 18 Feb 2015 10:00:04 +0025 Date: Wed, 18 Feb 2015 10:00:03 +0000 From: Bruce Richardson To: "Ananyev, Konstantin" Message-ID: <20150218100003.GA14728@bricha3-MOBL3> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2601191342CEEE43887BDE71AB977258213EF5E4@irsmsx105.ger.corp.intel.com> Organization: Intel Shannon Ltd. User-Agent: Mutt/1.5.23 (2014-03-12) 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 10:00:10 -0000 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 refcnt > > > >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 applications > > > 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/ RTE_MBUF_FROM_BADDR macros. > They are still there, for example rte_pktmbuf_detach() still uses it to restore mbuf's buf_addr. > The only principal change here, is that we don't rely more on RTE_MBUF_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) != (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 level? /Bruce > > > > > > Another idea would be to add a field in indirect mbufs that stores > > > the pointer to the "parent" mbuf. > > > > > > Regards, > > > Olivier > > >