From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f66.google.com (mail-wm0-f66.google.com [74.125.82.66]) by dpdk.org (Postfix) with ESMTP id 1435F98 for ; Tue, 21 Feb 2017 18:04:49 +0100 (CET) Received: by mail-wm0-f66.google.com with SMTP id r18so20812176wmd.3 for ; Tue, 21 Feb 2017 09:04:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=YZbYvPTKqTsLr1vxfPnqsyAKM+4DdKnUAnDk3AZY0fw=; b=cQEVjrlPendIN/oThYZ4N6LgSVLgKFzJOD3CFyFPP4sA6TY2ININF8ls+CU1l3yhaC tc/G+vbWiUKmloNLVcxK0c+fcNl9DMM4W4thIP+5e7NGJ3ZpupkZyfapOIaXFa7ZNoQE eRUiAgUyGoLZIJ0esSDA0tjYte4JFdblrGrF0Lma4sLZz3on8fyoaDtI9vCZ62Znuwk/ /f7ZygpbDxii6rwlkEfgqqTlzOfcanvMYLY81vdp/PnCqY2vqGA0tl08AWGxSZD+vsfS qmyBZFpfg4HdkZgtBbpvrkW4s/sMxZhQZeeYyD4NeUOKblk7X6SRSPENXdyyZKeDDzfC 9BwA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=YZbYvPTKqTsLr1vxfPnqsyAKM+4DdKnUAnDk3AZY0fw=; b=b2TgA59yOZ5ltXEuNqgYlksy/vE6Lvz0/onnetF1BnIbaYdEoi8OPWuMlWF3ErnhUb /Hk3MfPZnT4yIfNxpxm3vqEmvdsW/P4klAaT8/f2Ci049MBCVoqWQQI4fCA7tYZbHEc/ Kqv9AZXx3BYj5ZwmWemFvrZE31TnVILXJXSgHRKQtEkMy8ibIhJmgsC7CDqwHFAPPZ80 9/k9sNxnevyVcras2q0OmBZMwXNuiKw/jtdrvNZd7KElUnzUHi3kPwCSVbgqXfnQaSsJ vtTwSpQCIX9dg5tzofddtVVEzoBfX8h1RTc9qhG4ykxMY5/QemsDpvF4uweeQyeCDMLB nSSA== X-Gm-Message-State: AMke39k7s5H745ud3Y5AJ9qvzxDUq7K0sC4ooVJvMuEmO0RBw2dayzleFY2c8Z/hR/mMUOaAMRS8G4StxzmyWw== X-Received: by 10.28.135.82 with SMTP id j79mr25604996wmd.19.1487696689634; Tue, 21 Feb 2017 09:04:49 -0800 (PST) MIME-Version: 1.0 Sender: jblunck@gmail.com Received: by 10.28.211.20 with HTTP; Tue, 21 Feb 2017 09:04:48 -0800 (PST) In-Reply-To: <20170221163808.GA213576@bricha3-MOBL3.ger.corp.intel.com> References: <1485271173-13408-1-git-send-email-olivier.matz@6wind.com> <2601191342CEEE43887BDE71AB9772583F111A29@irsmsx105.ger.corp.intel.com> <20170216144807.7add2c71@platinum> <20170217115153.0afeb061@platinum> <20170217151708.20bf4a49@platinum> <20170221105400.2eba4747@glumotte.dev.6wind.com> <20170221163808.GA213576@bricha3-MOBL3.ger.corp.intel.com> From: Jan Blunck Date: Tue, 21 Feb 2017 18:04:48 +0100 X-Google-Sender-Auth: mFa9b2nKstbML-W0r1TK3gnr8yA Message-ID: To: Bruce Richardson Cc: Olivier MATZ , "Ananyev, Konstantin" , "dev@dpdk.org" Content-Type: text/plain; charset=UTF-8 Subject: Re: [dpdk-dev] [RFC 0/8] mbuf: structure reorganization X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 21 Feb 2017 17:04:50 -0000 On Tue, Feb 21, 2017 at 5:38 PM, Bruce Richardson wrote: > On Tue, Feb 21, 2017 at 05:12:12PM +0100, Jan Blunck wrote: >> >> Access through PMD specific function pointers should be relatively >> fast on access. Modern architecture optimize that use case well >> enough. >> > The cost of doing a function call per packet to access data starts to > add up very, very fast. For the app, once the data is written to the > mbuf, it should be in the L1 cache, giving very fast access to it in a > few cycles. However, if a function call has to be made in order to do > the read, that makes the read of that field many times more expensive. > Exactly. Right now the timestamp normalization is done before writing to each mbuf. Timestamps are usually read at most once ... if at all. If you look at the analysis use cases they are read to be written to persistent storage. My impression is we optimize this on the wrong end.