From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1F9CCA9EAF for ; Mon, 21 Oct 2019 20:10:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B1CFF20882 for ; Mon, 21 Oct 2019 20:10:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730267AbfJUUK2 (ORCPT ); Mon, 21 Oct 2019 16:10:28 -0400 Received: from mga12.intel.com ([192.55.52.136]:57609 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726672AbfJUUK2 (ORCPT ); Mon, 21 Oct 2019 16:10:28 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Oct 2019 13:10:27 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.67,324,1566889200"; d="scan'208";a="201468756" Received: from unknown (HELO [10.241.228.144]) ([10.241.228.144]) by orsmga006.jf.intel.com with ESMTP; 21 Oct 2019 13:10:26 -0700 Subject: Re: [Intel-wired-lan] FW: [PATCH bpf-next 2/4] xsk: allow AF_XDP sockets to receive packets directly from a queue To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= Cc: Alexei Starovoitov , Jakub Kicinski , Netdev , intel-wired-lan , "Herbert, Tom" , "Fijalkowski, Maciej" , "bpf@vger.kernel.org" , =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , "Karlsson, Magnus" References: <1570515415-45593-3-git-send-email-sridhar.samudrala@intel.com> <3ED8E928C4210A4289A677D2FEB48235140134CE@fmsmsx111.amr.corp.intel.com> <2bc26acd-170d-634e-c066-71557b2b3e4f@intel.com> <2032d58c-916f-d26a-db14-bd5ba6ad92b9@intel.com> <20191019001449.fk3gnhih4nx724pm@ast-mbp> <6f281517-3785-ce46-65de-e2f78576783b@intel.com> <20191019022525.w5xbwkav2cpqkfwi@ast-mbp> <877e4zd8py.fsf@toke.dk> From: "Samudrala, Sridhar" Message-ID: <7642a460-9ba3-d9f7-6cf8-aac45c7eef0d@intel.com> Date: Mon, 21 Oct 2019 13:10:26 -0700 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 10/20/2019 10:12 AM, Björn Töpel wrote: > On Sun, 20 Oct 2019 at 12:15, Toke Høiland-Jørgensen wrote: >> >> Alexei Starovoitov writes: >> >>> On Fri, Oct 18, 2019 at 05:45:26PM -0700, Samudrala, Sridhar wrote: >>>> On 10/18/2019 5:14 PM, Alexei Starovoitov wrote: >>>>> On Fri, Oct 18, 2019 at 11:40:07AM -0700, Samudrala, Sridhar wrote: >>>>>> >>>>>> Perf report for "AF_XDP default rxdrop" with patched kernel - mitigations ON >>>>>> ========================================================================== >>>>>> Samples: 44K of event 'cycles', Event count (approx.): 38532389541 >>>>>> Overhead Command Shared Object Symbol >>>>>> 15.31% ksoftirqd/28 [i40e] [k] i40e_clean_rx_irq_zc >>>>>> 10.50% ksoftirqd/28 bpf_prog_80b55d8a76303785 [k] bpf_prog_80b55d8a76303785 >>>>>> 9.48% xdpsock [i40e] [k] i40e_clean_rx_irq_zc >>>>>> 8.62% xdpsock xdpsock [.] main >>>>>> 7.11% ksoftirqd/28 [kernel.vmlinux] [k] xsk_rcv >>>>>> 5.81% ksoftirqd/28 [kernel.vmlinux] [k] xdp_do_redirect >>>>>> 4.46% xdpsock bpf_prog_80b55d8a76303785 [k] bpf_prog_80b55d8a76303785 >>>>>> 3.83% xdpsock [kernel.vmlinux] [k] xsk_rcv >>>>> >>>>> why everything is duplicated? >>>>> Same code runs in different tasks ? >>>> >>>> Yes. looks like these functions run from both the app(xdpsock) context and ksoftirqd context. >>>> >>>>> >>>>>> 2.81% ksoftirqd/28 [kernel.vmlinux] [k] bpf_xdp_redirect_map >>>>>> 2.78% ksoftirqd/28 [kernel.vmlinux] [k] xsk_map_lookup_elem >>>>>> 2.44% xdpsock [kernel.vmlinux] [k] xdp_do_redirect >>>>>> 2.19% ksoftirqd/28 [kernel.vmlinux] [k] __xsk_map_redirect >>>>>> 1.62% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_peek_addr >>>>>> 1.57% xdpsock [kernel.vmlinux] [k] xsk_umem_peek_addr >>>>>> 1.32% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu >>>>>> 1.28% xdpsock [kernel.vmlinux] [k] bpf_xdp_redirect_map >>>>>> 1.15% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_device >>>>>> 1.12% xdpsock [kernel.vmlinux] [k] xsk_map_lookup_elem >>>>>> 1.06% xdpsock [kernel.vmlinux] [k] __xsk_map_redirect >>>>>> 0.94% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_device >>>>>> 0.75% ksoftirqd/28 [kernel.vmlinux] [k] __x86_indirect_thunk_rax >>>>>> 0.66% ksoftirqd/28 [i40e] [k] i40e_clean_programming_status >>>>>> 0.64% ksoftirqd/28 [kernel.vmlinux] [k] net_rx_action >>>>>> 0.64% swapper [kernel.vmlinux] [k] intel_idle >>>>>> 0.62% ksoftirqd/28 [i40e] [k] i40e_napi_poll >>>>>> 0.57% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu >>>>>> >>>>>> Perf report for "AF_XDP direct rxdrop" with patched kernel - mitigations ON >>>>>> ========================================================================== >>>>>> Samples: 46K of event 'cycles', Event count (approx.): 38387018585 >>>>>> Overhead Command Shared Object Symbol >>>>>> 21.94% ksoftirqd/28 [i40e] [k] i40e_clean_rx_irq_zc >>>>>> 14.36% xdpsock xdpsock [.] main >>>>>> 11.53% ksoftirqd/28 [kernel.vmlinux] [k] xsk_rcv >>>>>> 11.32% xdpsock [i40e] [k] i40e_clean_rx_irq_zc >>>>>> 4.02% xdpsock [kernel.vmlinux] [k] xsk_rcv >>>>>> 2.91% ksoftirqd/28 [kernel.vmlinux] [k] xdp_do_redirect >>>>>> 2.45% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_peek_addr >>>>>> 2.19% xdpsock [kernel.vmlinux] [k] xsk_umem_peek_addr >>>>>> 2.08% ksoftirqd/28 [kernel.vmlinux] [k] bpf_direct_xsk >>>>>> 2.07% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu >>>>>> 1.53% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_device >>>>>> 1.39% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_device >>>>>> 1.22% ksoftirqd/28 [kernel.vmlinux] [k] xdp_get_xsk_from_qid >>>>>> 1.12% ksoftirqd/28 [i40e] [k] i40e_clean_programming_status >>>>>> 0.96% ksoftirqd/28 [i40e] [k] i40e_napi_poll >>>>>> 0.95% ksoftirqd/28 [kernel.vmlinux] [k] net_rx_action >>>>>> 0.89% xdpsock [kernel.vmlinux] [k] xdp_do_redirect >>>>>> 0.83% swapper [i40e] [k] i40e_clean_rx_irq_zc >>>>>> 0.70% swapper [kernel.vmlinux] [k] intel_idle >>>>>> 0.66% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu >>>>>> 0.60% xdpsock [kernel.vmlinux] [k] bpf_direct_xsk >>>>>> 0.50% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_discard_addr >>>>>> >>>>>> Based on the perf reports comparing AF_XDP default and direct rxdrop, we can say that >>>>>> AF_XDP direct rxdrop codepath is avoiding the overhead of going through these functions >>>>>> bpf_prog_xxx >>>>>> bpf_xdp_redirect_map >>>>>> xsk_map_lookup_elem >>>>>> __xsk_map_redirect >>>>>> With AF_XDP direct, xsk_rcv() is directly called via bpf_direct_xsk() in xdp_do_redirect() >>>>> >>>>> I don't think you're identifying the overhead correctly. >>>>> xsk_map_lookup_elem is 1% >>>>> but bpf_xdp_redirect_map() suppose to call __xsk_map_lookup_elem() >>>>> which is a different function: >>>>> ffffffff81493fe0 T __xsk_map_lookup_elem >>>>> ffffffff81492e80 t xsk_map_lookup_elem >>>>> >>>>> 10% for bpf_prog_80b55d8a76303785 is huge. >>>>> It's the actual code of the program _without_ any helpers. >>>>> How does the program actually look? >>>> >>>> It is the xdp program that is loaded via xsk_load_xdp_prog() in tools/lib/bpf/xsk.c >>>> https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next.git/tree/tools/lib/bpf/xsk.c#n268 >>> >>> I see. Looks like map_gen_lookup was never implemented for xskmap. >>> How about adding it first the way array_map_gen_lookup() is implemented? >>> This will easily give 2x perf gain. >> >> I guess we should implement this for devmaps as well now that we allow >> lookups into those. >> >> However, in this particular example, the lookup from BPF is not actually >> needed, since bpf_redirect_map() will return a configurable error value >> when the map lookup fails (for exactly this use case). >> >> So replacing: >> >> if (bpf_map_lookup_elem(&xsks_map, &index)) >> return bpf_redirect_map(&xsks_map, index, 0); >> >> with simply >> >> return bpf_redirect_map(&xsks_map, index, XDP_PASS); >> >> would save the call to xsk_map_lookup_elem(). >> > > Thanks for the reminder! I just submitted a patch. Still, doing the > map_gen_lookup() for xsk/devmaps still makes sense! > I tried Bjorn's patch that avoids the lookups in the BPF prog. https://lore.kernel.org/netdev/20191021105938.11820-1-bjorn.topel@gmail.com/ With this patch I am also seeing around 3-4% increase in xdpsock rxdrop performance and the perf report looks like this. Samples: 44K of event 'cycles', Event count (approx.): 38749965204 Overhead Command Shared Object Symbol 16.06% ksoftirqd/28 [i40e] [k] i40e_clean_rx_irq_zc 10.18% ksoftirqd/28 bpf_prog_3c8251c7e0fef8db [k] bpf_prog_3c8251c7e0fef8db 10.15% xdpsock [i40e] [k] i40e_clean_rx_irq_zc 10.06% ksoftirqd/28 [kernel.vmlinux] [k] xsk_rcv 7.45% xdpsock xdpsock [.] main 5.76% ksoftirqd/28 [kernel.vmlinux] [k] xdp_do_redirect 4.51% xdpsock bpf_prog_3c8251c7e0fef8db [k] bpf_prog_3c8251c7e0fef8db 3.67% xdpsock [kernel.vmlinux] [k] xsk_rcv 3.06% ksoftirqd/28 [kernel.vmlinux] [k] bpf_xdp_redirect_map 2.34% ksoftirqd/28 [kernel.vmlinux] [k] __xsk_map_redirect 2.33% xdpsock [kernel.vmlinux] [k] xdp_do_redirect 1.69% ksoftirqd/28 [kernel.vmlinux] [k] xsk_umem_peek_addr 1.69% xdpsock [kernel.vmlinux] [k] xsk_umem_peek_addr 1.42% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu 1.19% xdpsock [kernel.vmlinux] [k] bpf_xdp_redirect_map 1.13% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_device 0.95% ksoftirqd/28 [kernel.vmlinux] [k] dma_direct_sync_single_for_device 0.92% swapper [kernel.vmlinux] [k] intel_idle 0.92% xdpsock [kernel.vmlinux] [k] __xsk_map_redirect 0.80% ksoftirqd/28 [kernel.vmlinux] [k] __x86_indirect_thunk_rax 0.73% ksoftirqd/28 [i40e] [k] i40e_clean_programming_status 0.71% ksoftirqd/28 [kernel.vmlinux] [k] __xsk_map_lookup_elem 0.63% ksoftirqd/28 [kernel.vmlinux] [k] net_rx_action 0.62% ksoftirqd/28 [i40e] [k] i40e_napi_poll 0.58% xdpsock [kernel.vmlinux] [k] dma_direct_sync_single_for_cpu So with this patch applied, direct receive performance improvement comes down from 46% to 42%. I think it is still substantial enough to provide an option to allow direct receive for certain use cases. If it is OK, i can re-spin and submit the patches on top of the latest bpf-next Thanks Sridhar