From patchwork Tue Mar 21 13:47:11 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jesper Dangaard Brouer X-Patchwork-Id: 13182790 X-Patchwork-Delegate: bpf@iogearbox.net Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66DBAC6FD1D for ; Tue, 21 Mar 2023 13:49:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229696AbjCUNt2 (ORCPT ); Tue, 21 Mar 2023 09:49:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45366 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231220AbjCUNtW (ORCPT ); Tue, 21 Mar 2023 09:49:22 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id AD2ED457D5 for ; Tue, 21 Mar 2023 06:48:22 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679406501; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=7XInFRBUHO3MAh9r7zJFmhOIJ9vpsIZWXbrw7tTwZk8=; b=LZnt2hYWxX83FENAU2KuCsAEOcXKC7V18R3XB9hfdtHEcdFGmcvUl1+YbHW139uQJc1P9l u1UADTcVZKaUIubqV706oCXBvWcPXM69yfLAyVSTEtUNxJzUr19rbnfO1grn61G3ltbGAx XDC6+7l5oXpoAnk6FJ49hTWxyUN0puE= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-2-m6fLM9DzOWS9TtWpFcAgtg-1; Tue, 21 Mar 2023 09:47:13 -0400 X-MC-Unique: m6fLM9DzOWS9TtWpFcAgtg-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 9497F2806042; Tue, 21 Mar 2023 13:47:12 +0000 (UTC) Received: from firesoul.localdomain (unknown [10.45.242.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id 3B45B40C6E67; Tue, 21 Mar 2023 13:47:12 +0000 (UTC) Received: from [10.1.1.1] (localhost [IPv6:::1]) by firesoul.localdomain (Postfix) with ESMTP id A475130721A6C; Tue, 21 Mar 2023 14:47:11 +0100 (CET) Subject: [PATCH bpf-next V2 2/6] selftests/bpf: xdp_hw_metadata track more timestamps From: Jesper Dangaard Brouer To: bpf@vger.kernel.org Cc: Jesper Dangaard Brouer , netdev@vger.kernel.org, Stanislav Fomichev , martin.lau@kernel.org, ast@kernel.org, daniel@iogearbox.net, alexandr.lobakin@intel.com, larysa.zaremba@intel.com, xdp-hints@xdp-project.net, anthony.l.nguyen@intel.com, yoong.siang.song@intel.com, boon.leong.ong@intel.com, intel-wired-lan@lists.osuosl.org, pabeni@redhat.com, jesse.brandeburg@intel.com, kuba@kernel.org, edumazet@google.com, john.fastabend@gmail.com, hawk@kernel.org, davem@davemloft.net Date: Tue, 21 Mar 2023 14:47:11 +0100 Message-ID: <167940643162.2718137.8570573496056995556.stgit@firesoul> In-Reply-To: <167940634187.2718137.10209374282891218398.stgit@firesoul> References: <167940634187.2718137.10209374282891218398.stgit@firesoul> User-Agent: StGit/1.4 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org X-Patchwork-Delegate: bpf@iogearbox.net To correlate the hardware RX timestamp with something, add tracking of two software timestamps both clock source CLOCK_TAI (see description in man clock_gettime(2)). XDP metadata is extended with xdp_timestamp for capturing when XDP received the packet. Populated with BPF helper bpf_ktime_get_tai_ns(). I could not find a BPF helper for getting CLOCK_REALTIME, which would have been preferred. In userspace when AF_XDP sees the packet another software timestamp is recorded via clock_gettime() also clock source CLOCK_TAI. Example output shortly after loading igc driver: poll: 1 (0) xsk_ring_cons__peek: 1 0x11fc958: rx_desc[7]->addr=10000000000f000 addr=f100 comp_addr=f000 rx_hash: 0x00000000 rx_timestamp: 1676297171760293047 (sec:1676297171.7603) XDP RX-time: 1676297208760355863 (sec:1676297208.7604) delta sec:37.0001 AF_XDP time: 1676297208760416292 (sec:1676297208.7604) delta sec:0.0001 (60.429 usec) 0x11fc958: complete idx=15 addr=f000 The first observation is that the 37 sec difference between RX HW vs XDP timestamps, which indicate hardware is likely clock source CLOCK_REALTIME, because (as of this writing) CLOCK_TAI is initialised with a 37 sec offset. The 60 usec (microsec) difference between XDP vs AF_XDP userspace is the userspace wakeup time. On this hardware it was caused by CPU idle sleep states, which can be reduced by tuning /dev/cpu_dma_latency. View current requested/allowed latency bound via: hexdump --format '"%d\n"' /dev/cpu_dma_latency More explanation of the output and how this can be used to identify clock drift for the HW clock can be seen here[1]: [1] https://github.com/xdp-project/xdp-project/blob/master/areas/hints/xdp_hints_kfuncs02_driver_igc.org Signed-off-by: Jesper Dangaard Brouer Acked-by: Stanislav Fomichev --- .../testing/selftests/bpf/progs/xdp_hw_metadata.c | 9 +++- tools/testing/selftests/bpf/xdp_hw_metadata.c | 46 ++++++++++++++++++-- tools/testing/selftests/bpf/xdp_metadata.h | 1 3 files changed, 48 insertions(+), 8 deletions(-) diff --git a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c index 4c55b4d79d3d..40c17adbf483 100644 --- a/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c +++ b/tools/testing/selftests/bpf/progs/xdp_hw_metadata.c @@ -69,10 +69,13 @@ int rx(struct xdp_md *ctx) return XDP_PASS; } - if (!bpf_xdp_metadata_rx_timestamp(ctx, &meta->rx_timestamp)) - bpf_printk("populated rx_timestamp with %llu", meta->rx_timestamp); - else + if (!bpf_xdp_metadata_rx_timestamp(ctx, &meta->rx_timestamp)) { + meta->xdp_timestamp = bpf_ktime_get_tai_ns(); + bpf_printk("populated rx_timestamp with %llu", meta->rx_timestamp); + bpf_printk("populated xdp_timestamp with %llu", meta->xdp_timestamp); + } else { meta->rx_timestamp = 0; /* Used by AF_XDP as not avail signal */ + } if (!bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash)) bpf_printk("populated rx_hash with %u", meta->rx_hash); diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c index 1c8acb68b977..400bfe19abfe 100644 --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c @@ -27,6 +27,7 @@ #include #include #include +#include #include "xdp_metadata.h" @@ -134,14 +135,47 @@ static void refill_rx(struct xsk *xsk, __u64 addr) } } -static void verify_xdp_metadata(void *data) +#define NANOSEC_PER_SEC 1000000000 /* 10^9 */ +static __u64 gettime(clockid_t clock_id) +{ + struct timespec t; + int res; + + /* See man clock_gettime(2) for type of clock_id's */ + res = clock_gettime(clock_id, &t); + + if (res < 0) + error(res, errno, "Error with clock_gettime()"); + + return (__u64) t.tv_sec * NANOSEC_PER_SEC + t.tv_nsec; +} + +static void verify_xdp_metadata(void *data, clockid_t clock_id) { struct xdp_meta *meta; meta = data - sizeof(*meta); - printf("rx_timestamp: %llu\n", meta->rx_timestamp); printf("rx_hash: %u\n", meta->rx_hash); + printf("rx_timestamp: %llu (sec:%0.4f)\n", meta->rx_timestamp, + (double)meta->rx_timestamp / NANOSEC_PER_SEC); + if (meta->rx_timestamp) { + __u64 usr_clock = gettime(clock_id); + __u64 xdp_clock = meta->xdp_timestamp; + __s64 delta_X = xdp_clock - meta->rx_timestamp; + __s64 delta_X2U = usr_clock - xdp_clock; + + printf("XDP RX-time: %llu (sec:%0.4f) delta sec:%0.4f (%0.3f usec)\n", + xdp_clock, (double)xdp_clock / NANOSEC_PER_SEC, + (double)delta_X / NANOSEC_PER_SEC, + (double)delta_X / 1000); + + printf("AF_XDP time: %llu (sec:%0.4f) delta sec:%0.4f (%0.3f usec)\n", + usr_clock, (double)usr_clock / NANOSEC_PER_SEC, + (double)delta_X2U / NANOSEC_PER_SEC, + (double)delta_X2U / 1000); + } + } static void verify_skb_metadata(int fd) @@ -189,7 +223,7 @@ static void verify_skb_metadata(int fd) printf("skb hwtstamp is not found!\n"); } -static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd) +static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t clock_id) { const struct xdp_desc *rx_desc; struct pollfd fds[rxq + 1]; @@ -237,7 +271,8 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd) addr = xsk_umem__add_offset_to_addr(rx_desc->addr); printf("%p: rx_desc[%u]->addr=%llx addr=%llx comp_addr=%llx\n", xsk, idx, rx_desc->addr, addr, comp_addr); - verify_xdp_metadata(xsk_umem__get_data(xsk->umem_area, addr)); + verify_xdp_metadata(xsk_umem__get_data(xsk->umem_area, addr), + clock_id); xsk_ring_cons__release(&xsk->rx, 1); refill_rx(xsk, comp_addr); } @@ -364,6 +399,7 @@ static void timestamping_enable(int fd, int val) int main(int argc, char *argv[]) { + clockid_t clock_id = CLOCK_TAI; int server_fd = -1; int ret; int i; @@ -437,7 +473,7 @@ int main(int argc, char *argv[]) error(1, -ret, "bpf_xdp_attach"); signal(SIGINT, handle_signal); - ret = verify_metadata(rx_xsk, rxq, server_fd); + ret = verify_metadata(rx_xsk, rxq, server_fd, clock_id); close(server_fd); cleanup(); if (ret) diff --git a/tools/testing/selftests/bpf/xdp_metadata.h b/tools/testing/selftests/bpf/xdp_metadata.h index f6780fbb0a21..260345b2c6f1 100644 --- a/tools/testing/selftests/bpf/xdp_metadata.h +++ b/tools/testing/selftests/bpf/xdp_metadata.h @@ -11,5 +11,6 @@ struct xdp_meta { __u64 rx_timestamp; + __u64 xdp_timestamp; __u32 rx_hash; };