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GET /api/patches/3961/?format=api
{ "id": 3961, "url": "http://patches.dpdk.org/api/patches/3961/?format=api", "web_url": "http://patches.dpdk.org/project/dpdk/patch/1426004018-25948-7-git-send-email-stephen@networkplumber.org/", "project": { "id": 1, "url": "http://patches.dpdk.org/api/projects/1/?format=api", "name": "DPDK", "link_name": "dpdk", "list_id": "dev.dpdk.org", "list_email": "dev@dpdk.org", "web_url": "http://core.dpdk.org", "scm_url": "git://dpdk.org/dpdk", "webscm_url": "http://git.dpdk.org/dpdk", "list_archive_url": "https://inbox.dpdk.org/dev", "list_archive_url_format": "https://inbox.dpdk.org/dev/{}", "commit_url_format": "" }, "msgid": "<1426004018-25948-7-git-send-email-stephen@networkplumber.org>", "list_archive_url": "https://inbox.dpdk.org/dev/1426004018-25948-7-git-send-email-stephen@networkplumber.org", "date": "2015-03-10T16:13:38", "name": "[dpdk-dev,v2,6/6] rte_sched: eliminate floating point in calculating byte clock", "commit_ref": null, "pull_url": null, "state": "superseded", "archived": true, "hash": "0b810d5141337b233ef33baefaa3452018d45a4b", "submitter": { "id": 27, "url": "http://patches.dpdk.org/api/people/27/?format=api", "name": "Stephen Hemminger", "email": "stephen@networkplumber.org" }, "delegate": null, "mbox": "http://patches.dpdk.org/project/dpdk/patch/1426004018-25948-7-git-send-email-stephen@networkplumber.org/mbox/", "series": [], "comments": "http://patches.dpdk.org/api/patches/3961/comments/", "check": "pending", "checks": "http://patches.dpdk.org/api/patches/3961/checks/", "tags": {}, "related": [], "headers": { "Return-Path": "<dev-bounces@dpdk.org>", "X-Original-To": "patchwork@dpdk.org", "Delivered-To": "patchwork@dpdk.org", "Received": [ "from [92.243.14.124] (localhost [IPv6:::1])\n\tby dpdk.org (Postfix) with ESMTP id 0E6939AC1;\n\tTue, 10 Mar 2015 17:13:55 +0100 (CET)", "from mail-pd0-f173.google.com (mail-pd0-f173.google.com\n\t[209.85.192.173]) by dpdk.org (Postfix) with ESMTP id 7D40D9AB5\n\tfor <dev@dpdk.org>; Tue, 10 Mar 2015 17:13:52 +0100 (CET)", "by pdno5 with SMTP id o5so3434895pdn.1\n\tfor <dev@dpdk.org>; Tue, 10 Mar 2015 09:13:51 -0700 (PDT)", "from urahara.brocade.com\n\t(static-50-53-82-155.bvtn.or.frontiernet.net. [50.53.82.155])\n\tby mx.google.com with ESMTPSA id c8sm1836209pds.5.2015.03.10.09.13.50\n\t(version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128);\n\tTue, 10 Mar 2015 09:13:50 -0700 (PDT)" ], "X-Google-DKIM-Signature": "v=1; a=rsa-sha256; c=relaxed/relaxed;\n\td=1e100.net; s=20130820;\n\th=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to\n\t:references;\n\tbh=lmQNrlgmWDpgKOcCkoCt4Tj+CcANC+jDVODQh4nFvtc=;\n\tb=U/dKFdEk87Jrx0RZkHb/xosIFjjnv3I4wqm4TKcl4TSdQu73yaWEiRUhxjWMXzksdK\n\tGIHmtyY3znvZMnIMjwtlCyfvEEA1QnEUVk2CBohlNNf/WR1RVmUjy+znF/ep+eASkEiw\n\tvZB/jRBFUiv2DmhBHscd9PVnZVbhdsjcAQvBlbWU3tZ+vzVYZLiXj0FkVbtaDUJtvEYE\n\tSGjNWiN2J86pALtgmE/2PljsUQR8JfaSoeJnj3lOlxGmy98Spb3hdjOssRY9JD8f2AmZ\n\tb0QQcgIYJsLA16o3vnUN0GiHenoJhrt2hC8zJlEoyQBHD/t1+nfuwrKyL7E/FKhCMqgy\n\tg4Dg==", "X-Gm-Message-State": "ALoCoQkPpVdF1h67+PRUat1n6lrrFw4Mfk7I57xfIM7ew/MfQQJYTJYngMxlPSv2myrGO1ziBVzU", "X-Received": "by 10.66.221.135 with SMTP id qe7mr66186355pac.97.1426004031725; \n\tTue, 10 Mar 2015 09:13:51 -0700 (PDT)", "From": "Stephen Hemminger <stephen@networkplumber.org>", "To": "cristian.dumitrescu@intel.com", "Date": "Tue, 10 Mar 2015 09:13:38 -0700", "Message-Id": "<1426004018-25948-7-git-send-email-stephen@networkplumber.org>", "X-Mailer": "git-send-email 2.1.4", "In-Reply-To": "<1426004018-25948-1-git-send-email-stephen@networkplumber.org>", "References": "<1426004018-25948-1-git-send-email-stephen@networkplumber.org>", "Cc": "dev@dpdk.org, Stephen Hemminger <shemming@brocade.com>", "Subject": "[dpdk-dev] [PATCH v2 6/6] rte_sched: eliminate floating point in\n\tcalculating byte clock", "X-BeenThere": "dev@dpdk.org", "X-Mailman-Version": "2.1.15", "Precedence": "list", "List-Id": "patches and discussions about DPDK <dev.dpdk.org>", "List-Unsubscribe": "<http://dpdk.org/ml/options/dev>,\n\t<mailto:dev-request@dpdk.org?subject=unsubscribe>", "List-Archive": "<http://dpdk.org/ml/archives/dev/>", "List-Post": "<mailto:dev@dpdk.org>", "List-Help": "<mailto:dev-request@dpdk.org?subject=help>", "List-Subscribe": "<http://dpdk.org/ml/listinfo/dev>,\n\t<mailto:dev-request@dpdk.org?subject=subscribe>", "Errors-To": "dev-bounces@dpdk.org", "Sender": "\"dev\" <dev-bounces@dpdk.org>" }, "content": "From: Stephen Hemminger <shemming@brocade.com>\n\nThe old code was doing a floating point divide for each rte_dequeue()\nwhich is very expensive. Change to using fixed point scaled math instead.\nThis improved performance from 5Gbit/sec to 10 Gbit/sec\n\nSigned-off-by: Stephen Hemminger <stephen@networkplumber.org>\n---\nv2 -- no changes\n despite objections, the performance observation is real\n on Intel(R) Core(TM) i7-3770 CPU\n\n lib/librte_sched/rte_sched.c | 14 ++++++++++----\n 1 file changed, 10 insertions(+), 4 deletions(-)", "diff": "diff --git a/lib/librte_sched/rte_sched.c b/lib/librte_sched/rte_sched.c\nindex 74d0e0a..522a647 100644\n--- a/lib/librte_sched/rte_sched.c\n+++ b/lib/librte_sched/rte_sched.c\n@@ -102,6 +102,9 @@\n \n #define RTE_SCHED_BMP_POS_INVALID UINT32_MAX\n \n+/* For cycles_per_byte calculation */\n+#define RTE_SCHED_TIME_SHIFT\t\t 20\n+\n struct rte_sched_subport {\n \t/* Token bucket (TB) */\n \tuint64_t tb_time; /* time of last update */\n@@ -239,7 +242,7 @@ struct rte_sched_port {\n \tuint64_t time_cpu_cycles; /* Current CPU time measured in CPU cyles */\n \tuint64_t time_cpu_bytes; /* Current CPU time measured in bytes */\n \tuint64_t time; /* Current NIC TX time measured in bytes */\n-\tdouble cycles_per_byte; /* CPU cycles per byte */\n+\tuint32_t cycles_per_byte; /* CPU cycles per byte (scaled) */\n \n \t/* Scheduling loop detection */\n \tuint32_t pipe_loop;\n@@ -657,7 +660,9 @@ rte_sched_port_config(struct rte_sched_port_params *params)\n \tport->time_cpu_cycles = rte_get_tsc_cycles();\n \tport->time_cpu_bytes = 0;\n \tport->time = 0;\n-\tport->cycles_per_byte = ((double) rte_get_tsc_hz()) / ((double) params->rate);\n+\n+\tport->cycles_per_byte = (rte_get_tsc_hz() << RTE_SCHED_TIME_SHIFT)\n+\t\t/ params->rate;\n \n \t/* Scheduling loop detection */\n \tport->pipe_loop = RTE_SCHED_PIPE_INVALID;\n@@ -2126,11 +2131,12 @@ rte_sched_port_time_resync(struct rte_sched_port *port)\n {\n \tuint64_t cycles = rte_get_tsc_cycles();\n \tuint64_t cycles_diff = cycles - port->time_cpu_cycles;\n-\tdouble bytes_diff = ((double) cycles_diff) / port->cycles_per_byte;\n+\tuint64_t bytes_diff = (cycles_diff << RTE_SCHED_TIME_SHIFT)\n+\t\t/ port->cycles_per_byte;\n \n \t/* Advance port time */\n \tport->time_cpu_cycles = cycles;\n-\tport->time_cpu_bytes += (uint64_t) bytes_diff;\n+\tport->time_cpu_bytes += bytes_diff;\n \tif (port->time < port->time_cpu_bytes) {\n \t\tport->time = port->time_cpu_bytes;\n \t}\n", "prefixes": [ "dpdk-dev", "v2", "6/6" ] }