From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by dpdk.space (Postfix) with ESMTP id 32E4BA00E6 for ; Thu, 16 May 2019 22:37:50 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id DA91B5920; Thu, 16 May 2019 22:37:48 +0200 (CEST) Received: from mga03.intel.com (mga03.intel.com [134.134.136.65]) by dpdk.org (Postfix) with ESMTP id 54D6858EC for ; Thu, 16 May 2019 22:37:47 +0200 (CEST) X-Amp-Result: UNSCANNABLE X-Amp-File-Uploaded: False Received: from orsmga007.jf.intel.com ([10.7.209.58]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 16 May 2019 13:37:46 -0700 X-ExtLoop1: 1 Received: from bricha3-mobl.ger.corp.intel.com ([10.252.2.218]) by orsmga007.jf.intel.com with SMTP; 16 May 2019 13:37:44 -0700 Received: by (sSMTP sendmail emulation); Thu, 16 May 2019 21:37:43 +0100 Date: Thu, 16 May 2019 21:37:42 +0100 From: Bruce Richardson To: Stephen Hemminger Cc: dev@dpdk.org Message-ID: <20190516203742.GB642@bricha3-MOBL.ger.corp.intel.com> References: <20190515221952.21959-1-stephen@networkplumber.org> <20190515221952.21959-5-stephen@networkplumber.org> <20190516160337.GA632@bricha3-MOBL.ger.corp.intel.com> <20190516090652.5ad965f4@hermes.lan> <20190516160745.GB632@bricha3-MOBL.ger.corp.intel.com> <20190516163643.GC632@bricha3-MOBL.ger.corp.intel.com> <20190516100454.36e7bc88@hermes.lan> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190516100454.36e7bc88@hermes.lan> User-Agent: Mutt/1.11.4 (2019-03-13) Subject: Re: [dpdk-dev] [RFC 4/4] net/ether: use bitops to speedup comparison X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On Thu, May 16, 2019 at 10:04:54AM -0700, Stephen Hemminger wrote: > On Thu, 16 May 2019 17:36:43 +0100 > Bruce Richardson wrote: > > > On Thu, May 16, 2019 at 05:07:45PM +0100, Bruce Richardson wrote: > > > On Thu, May 16, 2019 at 09:06:52AM -0700, Stephen Hemminger wrote: > > > > On Thu, 16 May 2019 17:03:37 +0100 > > > > Bruce Richardson wrote: > > > > > > > > > On Wed, May 15, 2019 at 03:19:52PM -0700, Stephen Hemminger wrote: > > > > > > Using bit operations like or and xor is faster than a loop > > > > > > on all architectures. Really just explicit unrolling. > > > > > > > > > > > > Similar cast to uint16 unaligned is already done in > > > > > > other functions here. > > > > > > > > > > > > Signed-off-by: Stephen Hemminger > > > > > > --- > > > > > > lib/librte_net/rte_ether.h | 17 +++++++---------- > > > > > > 1 file changed, 7 insertions(+), 10 deletions(-) > > > > > > > > > > > Rather than casting to unaligned values, which gives compiler warnings in > > > > > some cases, I believe we should just mark the ethernet addresses as always > > > > > being 2-byte aligned and simplify things. [unless we have a good use case > > > > > where we won't have 2-byte alignment???]. > > > > > > > > > > See patch: http://patches.dpdk.org/patch/53482/ > > > > > > > > > > Regards, > > > > > /Bruce > > > > > > > > I agree. Then you could also remove the unaligned_uint16_t that > > > > already exists in rte_ether.h > > > > > > > > Do you want me to put your patch in my series? > > > > > > Sure, feel free. > > > > > > > I've just found another problem in this area. Compiling l2fwd with gcc 9, I > > get: > > > > main.c:164:54: warning: taking address of packed member of ‘struct ether_hdr’ may result in an unaligned pointer value [-Waddress-of-packed-member] > > 164 | ether_addr_copy(&l2fwd_ports_eth_addr[dest_portid], ð->s_addr); > > | > > > > Looking at some of the structures, it appears that not all the packet > > attributes may be necessary. For example, while AFAIK there are not > > absolute guarantees about structure padding, for all compilers I remember > > using the following changes are safe: > > > > diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h > > index 8090b7c01..7d9f34791 100644 > > --- a/lib/librte_net/rte_ether.h > > +++ b/lib/librte_net/rte_ether.h > > @@ -57,7 +57,7 @@ extern "C" { > > struct ether_addr { > > /** Addr bytes in tx order */ > > uint8_t addr_bytes[ETHER_ADDR_LEN] __rte_aligned(2); > > -} __attribute__((__packed__)); > > +}; > > > > #define ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */ > > #define ETHER_GROUP_ADDR 0x01 /**< Multicast or broadcast Eth. address. */ > > @@ -273,7 +273,7 @@ struct ether_hdr { > > struct ether_addr d_addr; /**< Destination address. */ > > struct ether_addr s_addr; /**< Source address. */ > > uint16_t ether_type; /**< Frame type. */ > > -} __attribute__((__packed__)); > > +}; > > > > /** > > * Ethernet VLAN Header. > > @@ -283,7 +283,7 @@ struct ether_hdr { > > struct vlan_hdr { > > uint16_t vlan_tci; /**< Priority (3) + CFI (1) + Identifier Code (12) */ > > uint16_t eth_proto;/**< Ethernet type of encapsulated frame. */ > > -} __attribute__((__packed__)); > > +}; > > > > /** > > * VXLAN protocol header. > > > > I think we therefore should consider removing those packed attributes to > > avoid application warnings. > > > > /Bruce > > Agree if structure is naturally packed, adding packed attribute is a mistake. Do you want to also include such a change in your patchset, or will I do up a patch for it - perhaps a two-patch set with this and my previous alignment patch?