From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olivier MATZ Subject: Re: [PATCH v2 03/20] i40e: call i40e_txd_enable_checksum only for offloaded packets Date: Wed, 11 Feb 2015 18:13:36 +0100 Message-ID: <54DB8DC0.500@6wind.com> References: <1422623775-8050-1-git-send-email-olivier.matz@6wind.com> <1423041925-26956-1-git-send-email-olivier.matz@6wind.com> <1423041925-26956-4-git-send-email-olivier.matz@6wind.com> <54DA3AB0.3040500@6wind.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit To: "Zhang, Helin" , "dev-VfR2kkLFssw@public.gmane.org" Return-path: In-Reply-To: List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" Hi Helin, On 02/11/2015 06:32 AM, Zhang, Helin wrote: >> On 02/10/2015 07:03 AM, Zhang, Helin wrote: >>>> /* Enable checksum offloading */ >>>> cd_tunneling_params = 0; >>>> - i40e_txd_enable_checksum(ol_flags, &td_cmd, &td_offset, >>>> - l2_len, l3_len, outer_l2_len, >>>> - outer_l3_len, >>>> - &cd_tunneling_params); >>>> + if (ol_flags & I40E_TX_CKSUM_OFFLOAD_MASK) { >>> likely should be added. >> >> I would say unlikely() instead. I think the non-offload case should be the default >> one. What do you think? Maybe you missed this comment. Any thoughts? >>>> + i40e_txd_enable_checksum(ol_flags, &td_cmd, &td_offset, >>>> + l2_len, l3_len, outer_l2_len, >>>> + outer_l3_len, >>>> + &cd_tunneling_params); >>>> + } >>> As this code changes are in fast path, performance regression test is >>> needed. I would like to see the performance difference with or without >>> this patch set. Hopefully nothing different. If you need any helps, just let me >> know. >> >> I'm sorry, I won't have the needed resources to bench this as I would have to >> setup a performance platform with i40e devices. >> >> But I'm pretty sure that the code in non-offload case would be faster with this >> patch as it will avoid many operations in i40e_txd_enable_checksum(). >> >> For the offload case, as we also removed the if (l2_len == 0) and if (l3_len == 0), >> I think there are also less tests than before my patch series. >> >> So in my opinion, adding this test does not really justify to check the >> performance. > As 40G is quite sensitive on cpu cycles, we'd better to avoid any performance drop > during our modifying the code for fast path. Performance is what we care about too > much. Based on my experiences, even minor code changes may result in big > performance impact. > It seems that we may need to help you on performance measurement. Thanks, indeed it's helpful if you can check performance non-regression. Regards, Olivier