From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id D5F7043EDB; Mon, 22 Apr 2024 17:24:05 +0200 (CEST) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 3591E40A77; Mon, 22 Apr 2024 17:23:54 +0200 (CEST) Received: from mail-pl1-f171.google.com (mail-pl1-f171.google.com [209.85.214.171]) by mails.dpdk.org (Postfix) with ESMTP id B1D9D406B7 for ; Mon, 22 Apr 2024 17:23:49 +0200 (CEST) Received: by mail-pl1-f171.google.com with SMTP id d9443c01a7336-1e8fce77bb2so20279565ad.0 for ; Mon, 22 Apr 2024 08:23:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=networkplumber-org.20230601.gappssmtp.com; s=20230601; t=1713799429; x=1714404229; darn=dpdk.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=5HM/cXHYCXkBcg/q7AXiLDL3B7YhqPX/DI3zJV9tOpE=; b=boWrbkMEXIuPsSrNv0r4HONNSJP/FSIFuTjM8B4RuZ6nxtEdA0FePocg+LCytWUej+ x/+SL7dbHSTqfFMvT4ogHB6sRTjmf2DH+ws01FlX6Lqz5oLJvXvOYi+Lnq4tp7z0OMyA ivMGZD0AKqNk5Ju12r2LU6ptXKQY/eGuUtz3wi4Y9gNsTBKhyskXaGWtDnbbMETMtTic vWGZDVWCOPRQMfw5/mdebb9NUqACMOUhGPqYYZLBAPffzeYgphzUesxmMaU7NadeUGS0 wUqj5IAPlRUs1xTo9G4unDPZJA1qsBVB/qB2R0AGWbMm/xpBbe1jguVOq6QsYRE/UI7I gsiw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713799429; x=1714404229; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=5HM/cXHYCXkBcg/q7AXiLDL3B7YhqPX/DI3zJV9tOpE=; b=ESqa8AbI3wQ7kfBFrXfA3em5+1xI20CJ9yW8sPzL5FTVrm0IxLwAuwJiki13WfNcZb +Cw5trioVlr36h/Gq8b3sWGql/zkwYoHKlHSyysAGR4lu9GrWbY1ThBwV+pdIxMPASfB E7ezza4MaxUXiVjtJoaeTSSr8yb8yRvqObghdiMmcuCvZatJTTjp4eiStC6293p0pdjp 6RhRbQBG0g9yzzxm02kdMU8F1GZkzRX9bml0h2/AUzHqc7lOFp+n/j2/wZQWnetWDLoN gdi7ygmSiQKlOTQySks3ZbA7wttJjEP4qXDPEySQH27/S0FcgN5W2jktlH2499J/pXo1 KaFg== X-Gm-Message-State: AOJu0Yz0jaRzk6TxU+8RXNwSnsrkBz9eI7kgcDr4rFQfRF1rZTNz7Xfy TwG+al5Nn7CKPs+x4Ae5Ce9GuRy4O81TQKwUL0fh8y+UXgWltEFFn9DzPDi7LzwYqDThfJYFsYI I X-Google-Smtp-Source: AGHT+IFf+TPWXIsHplFtuENczBwtefH0cCac8ErVNWe4A8iQIE9HJlWyTYcGr/b84zdNly0za1+++Q== X-Received: by 2002:a17:902:e742:b0:1ea:cc:b59e with SMTP id p2-20020a170902e74200b001ea00ccb59emr425712plf.19.1713799428904; Mon, 22 Apr 2024 08:23:48 -0700 (PDT) Received: from hermes.local (204-195-96-226.wavecable.com. [204.195.96.226]) by smtp.gmail.com with ESMTPSA id cb17-20020a056a02071100b0060063c4be3bsm1402783pgb.14.2024.04.22.08.23.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Apr 2024 08:23:48 -0700 (PDT) From: Stephen Hemminger To: dev@dpdk.org Cc: Stephen Hemminger , Tyler Retzlaff , =?UTF-8?q?Morten=20Br=C3=B8rup?= , Reshma Pattan Subject: [PATCH v5 3/9] latencystats: do not use floating point Date: Mon, 22 Apr 2024 08:21:33 -0700 Message-ID: <20240422152336.147553-4-stephen@networkplumber.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240422152336.147553-1-stephen@networkplumber.org> References: <20240408195036.182545-1-stephen@networkplumber.org> <20240422152336.147553-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org The cycle counts do not need to be stored as floating point. Instead keep track of latency in cycles, and convert to nanoseconds when read. Use scaled math with exponential Weighted Moving Average weight of .25 to avoid use of floating point for that. The average latency took too long to "warm up". Do what RFC 6298 suggests and initialize on first sample. Signed-off-by: Stephen Hemminger Acked-by: Tyler Retzlaff Acked-by: Morten Brørup --- lib/latencystats/rte_latencystats.c | 128 ++++++++++++++++------------ 1 file changed, 73 insertions(+), 55 deletions(-) diff --git a/lib/latencystats/rte_latencystats.c b/lib/latencystats/rte_latencystats.c index 3152256066..2140ab87c4 100644 --- a/lib/latencystats/rte_latencystats.c +++ b/lib/latencystats/rte_latencystats.c @@ -4,6 +4,7 @@ #include +#include #include #include #include @@ -41,11 +42,14 @@ static uint64_t samp_intvl; static uint64_t timer_tsc; static uint64_t prev_tsc; +#define LATENCY_AVG_SCALE 4 +#define LATENCY_JITTER_SCALE 16 + struct rte_latency_stats { - float min_latency; /**< Minimum latency in nano seconds */ - float avg_latency; /**< Average latency in nano seconds */ - float max_latency; /**< Maximum latency in nano seconds */ - float jitter; /** Latency variation */ + uint64_t min_latency; /**< Minimum latency */ + uint64_t avg_latency; /**< Average latency */ + uint64_t max_latency; /**< Maximum latency */ + uint64_t jitter; /** Latency variation */ rte_spinlock_t lock; /** Latency calculation lock */ }; @@ -61,31 +65,38 @@ static struct rxtx_cbs tx_cbs[RTE_MAX_ETHPORTS][RTE_MAX_QUEUES_PER_PORT]; struct latency_stats_nameoff { char name[RTE_ETH_XSTATS_NAME_SIZE]; unsigned int offset; + unsigned int scale; }; static const struct latency_stats_nameoff lat_stats_strings[] = { - {"min_latency_ns", offsetof(struct rte_latency_stats, min_latency)}, - {"avg_latency_ns", offsetof(struct rte_latency_stats, avg_latency)}, - {"max_latency_ns", offsetof(struct rte_latency_stats, max_latency)}, - {"jitter_ns", offsetof(struct rte_latency_stats, jitter)}, + {"min_latency_ns", offsetof(struct rte_latency_stats, min_latency), 1}, + {"avg_latency_ns", offsetof(struct rte_latency_stats, avg_latency), LATENCY_AVG_SCALE}, + {"max_latency_ns", offsetof(struct rte_latency_stats, max_latency), 1}, + {"jitter_ns", offsetof(struct rte_latency_stats, jitter), LATENCY_JITTER_SCALE}, }; #define NUM_LATENCY_STATS (sizeof(lat_stats_strings) / \ sizeof(lat_stats_strings[0])) -int32_t -rte_latencystats_update(void) +static void +latencystats_collect(uint64_t values[]) { unsigned int i; - float *stats_ptr = NULL; - uint64_t values[NUM_LATENCY_STATS] = {0}; - int ret; + const uint64_t *stats; for (i = 0; i < NUM_LATENCY_STATS; i++) { - stats_ptr = RTE_PTR_ADD(glob_stats, - lat_stats_strings[i].offset); - values[i] = floor(*stats_ptr / cycles_per_ns); + stats = RTE_PTR_ADD(glob_stats, lat_stats_strings[i].offset); + values[i] = floor(*stats / (cycles_per_ns * lat_stats_strings[i].scale)); } +} + +int32_t +rte_latencystats_update(void) +{ + uint64_t values[NUM_LATENCY_STATS]; + int ret; + + latencystats_collect(values); ret = rte_metrics_update_values(RTE_METRICS_GLOBAL, latency_stats_index, @@ -97,16 +108,16 @@ rte_latencystats_update(void) } static void -rte_latencystats_fill_values(struct rte_metric_value *values) +rte_latencystats_fill_values(struct rte_metric_value *metrics) { + uint64_t values[NUM_LATENCY_STATS]; unsigned int i; - float *stats_ptr = NULL; + + latencystats_collect(values); for (i = 0; i < NUM_LATENCY_STATS; i++) { - stats_ptr = RTE_PTR_ADD(glob_stats, - lat_stats_strings[i].offset); - values[i].key = i; - values[i].value = floor(*stats_ptr / cycles_per_ns); + metrics[i].key = i; + metrics[i].value = values[i]; } } @@ -151,15 +162,9 @@ calc_latency(uint16_t pid __rte_unused, void *_ __rte_unused) { unsigned int i; - uint64_t now; - float latency; - static float prev_latency; - /* - * Alpha represents degree of weighting decrease in EWMA, - * a constant smoothing factor between 0 and 1. The value - * is used below for measuring average latency. - */ - const float alpha = 0.2; + uint64_t now, latency; + static uint64_t prev_latency; + static bool first_sample = true; now = rte_rdtsc(); @@ -170,32 +175,45 @@ calc_latency(uint16_t pid __rte_unused, latency = now - *timestamp_dynfield(pkts[i]); - /* - * The jitter is calculated as statistical mean of interpacket - * delay variation. The "jitter estimate" is computed by taking - * the absolute values of the ipdv sequence and applying an - * exponential filter with parameter 1/16 to generate the - * estimate. i.e J=J+(|D(i-1,i)|-J)/16. Where J is jitter, - * D(i-1,i) is difference in latency of two consecutive packets - * i-1 and i. - * Reference: Calculated as per RFC 5481, sec 4.1, - * RFC 3393 sec 4.5, RFC 1889 sec. - */ - glob_stats->jitter += (fabsf(prev_latency - latency) - - glob_stats->jitter)/16; - if (glob_stats->min_latency == 0) - glob_stats->min_latency = latency; - else if (latency < glob_stats->min_latency) + if (unlikely(first_sample)) { + first_sample = false; + glob_stats->min_latency = latency; - else if (latency > glob_stats->max_latency) glob_stats->max_latency = latency; - /* - * The average latency is measured using exponential moving - * average, i.e. using EWMA - * https://en.wikipedia.org/wiki/Moving_average - */ - glob_stats->avg_latency += - alpha * (latency - glob_stats->avg_latency); + glob_stats->avg_latency = latency * 4; + /* start ad if previous sample had 0 latency */ + glob_stats->jitter = latency / LATENCY_JITTER_SCALE; + } else { + /* + * The jitter is calculated as statistical mean of interpacket + * delay variation. The "jitter estimate" is computed by taking + * the absolute values of the ipdv sequence and applying an + * exponential filter with parameter 1/16 to generate the + * estimate. i.e J=J+(|D(i-1,i)|-J)/16. Where J is jitter, + * D(i-1,i) is difference in latency of two consecutive packets + * i-1 and i. Jitter is scaled by 16. + * Reference: Calculated as per RFC 5481, sec 4.1, + * RFC 3393 sec 4.5, RFC 1889 sec. + */ + long long delta = prev_latency - latency; + glob_stats->jitter += llabs(delta) + - glob_stats->jitter / LATENCY_JITTER_SCALE; + + if (latency < glob_stats->min_latency) + glob_stats->min_latency = latency; + if (latency > glob_stats->max_latency) + glob_stats->max_latency = latency; + /* + * The average latency is measured using exponential moving + * average, i.e. using EWMA + * https://en.wikipedia.org/wiki/Moving_average + * + * Alpha is .25, avg_latency is scaled by 4. + */ + glob_stats->avg_latency += latency + - glob_stats->avg_latency / LATENCY_AVG_SCALE; + } + prev_latency = latency; } rte_spinlock_unlock(&glob_stats->lock); -- 2.43.0