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 B07D5B3A5 for ; Wed, 17 Sep 2014 17:59:41 +0200 (CEST) Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga101.jf.intel.com with ESMTP; 17 Sep 2014 09:03:51 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.04,540,1406617200"; d="scan'208";a="574492978" Received: from irsmsx103.ger.corp.intel.com ([163.33.3.157]) by orsmga001.jf.intel.com with ESMTP; 17 Sep 2014 09:02:08 -0700 Received: from irsmsx152.ger.corp.intel.com (163.33.192.66) by IRSMSX103.ger.corp.intel.com (163.33.3.157) with Microsoft SMTP Server (TLS) id 14.3.195.1; Wed, 17 Sep 2014 17:02:07 +0100 Received: from irsmsx103.ger.corp.intel.com ([169.254.3.112]) by IRSMSX152.ger.corp.intel.com ([169.254.6.48]) with mapi id 14.03.0195.001; Wed, 17 Sep 2014 17:02:08 +0100 From: "Richardson, Bruce" To: Neil Horman Thread-Topic: [dpdk-dev] [PATCH 4/5] mbuf: add userdata pointer field Thread-Index: AQHP0l6Is28HwrbvRkaWBwsjE0afXZwFZG0AgAAWEJA= Date: Wed, 17 Sep 2014 16:02:07 +0000 Message-ID: <59AF69C657FD0841A61C55336867B5B0343F2F91@IRSMSX103.ger.corp.intel.com> References: <1410948102-12740-1-git-send-email-bruce.richardson@intel.com> <1410948102-12740-5-git-send-email-bruce.richardson@intel.com> <20140917153510.GG4213@localhost.localdomain> In-Reply-To: <20140917153510.GG4213@localhost.localdomain> Accept-Language: en-GB, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [163.33.239.180] 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 4/5] mbuf: add userdata pointer field 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, 17 Sep 2014 15:59:42 -0000 > -----Original Message----- > From: Neil Horman [mailto:nhorman@tuxdriver.com] > Sent: Wednesday, September 17, 2014 4:35 PM > To: Richardson, Bruce > Cc: dev@dpdk.org > Subject: Re: [dpdk-dev] [PATCH 4/5] mbuf: add userdata pointer field >=20 > On Wed, Sep 17, 2014 at 11:01:41AM +0100, Bruce Richardson wrote: > > While some applications may store metadata about packets in the packet > > mbuf headroom, this is not a workable solution for packet metadata whic= h > > is either: > > * larger than the headroom (or headroom is needed for adding pkt header= s) > > * needs to be shared or copied among packets > > > > To support these use cases in applications, we reserve a general > > "userdata" pointer field inside the second cache-line of the mbuf. This > > is better than having the application store the pointer to the external > > metadata in the packet headroom, as it saves an additional cache-line > > from being used. > > > > Apart from storing metadata, this field also provides a general 8-byte > > scratch space inside the mbuf for any other application uses that are > > applicable. > > > > Signed-off-by: Bruce Richardson > > --- > > lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h | 3 ++- > > lib/librte_mbuf/rte_mbuf.h | 3 +++ > > 2 files changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_commo= n.h > b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h > > index 25ed672..d27e891 100644 > > --- a/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h > > +++ b/lib/librte_eal/linuxapp/eal/include/exec-env/rte_kni_common.h > > @@ -117,7 +117,8 @@ struct rte_kni_mbuf { > > uint16_t data_len; /**< Amount of data in segment buffer. */ > > uint32_t pkt_len; /**< Total pkt len: sum of all segment data_l= en. */ > > char pad3[8]; > > - void *pool __attribute__((__aligned__(64))); > > + void *pad4 __attribute__((__aligned__(64))); > > + void *pool; > I don't see a comment about this in the changelog, only about the userdat= a > pointer being added below. Yes, this is the userdata pointer - just added as padding here, since it's = not actually needed by the kernel-side KNI module. >=20 >=20 > > void *next; > > }; > > > > diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h > > index 8e27d2e..b1acfc3 100644 > > --- a/lib/librte_mbuf/rte_mbuf.h > > +++ b/lib/librte_mbuf/rte_mbuf.h > > @@ -172,6 +172,9 @@ struct rte_mbuf { > > > > /* second cache line - fields only used in slow path or on TX */ > > MARKER cacheline1 __rte_cache_aligned; > > + > > + void *userdata; /**< Can be used for external metadata */ > > + > Do you want to make this a void* or a char[8]? I ask because if people a= re > going to use is as a scratch space (rather than a pointer), they get a su= prise > when they build this on 32 bit systems, and their 8 byte scratch space is > reduced to 4 bytes. I think this is better as a pointer, as that is how it is likely to be used= . As for 32-bit, I'm torn between wanting to just update the comment and fe= eling the need to update the code to actually make the thing 8-byte on 32-b= it! Changing the comment to be more accurate is easier, unions are ugly loo= king in the structure IMHO, so maybe I'll just mark the following field (po= ol) as always 8-byte aligned.... /Bruce >=20 > Neil >=20 > > struct rte_mempool *pool; /**< Pool from which mbuf was allocated. > */ > > struct rte_mbuf *next; /**< Next segment of scattered packet. */ > > > > -- > > 1.9.3 > > > >