From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f172.google.com (mail-wi0-f172.google.com [209.85.212.172]) by dpdk.org (Postfix) with ESMTP id 49CDBC320 for ; Wed, 20 May 2015 16:45:21 +0200 (CEST) Received: by wicmc15 with SMTP id mc15so152214785wic.1 for ; Wed, 20 May 2015 07:45:21 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:cc:subject:date:message-id:organization :user-agent:in-reply-to:references:mime-version :content-transfer-encoding:content-type; bh=A18hwC1sWdgaxjzxP0ccd7nR1WFq9HQ2kzUiRHc36dE=; b=XqvgsGjvd9oBluGmEIOzDArydNo4YXdS7w6DcYMipA4RoLkoEWhiX51QVJYViyUr3C OpSwgMxH+/UafHEWp+DAgdxF/seBYwE38S2aqjkIXr71CZhCFqGXUtrF8v7PTNRjpgT4 C9mHn/UC4NSgWRyFbyJEwWcSj3PDQP4K3kHJO4UI6MsePy9O945iaOb8mNt5b7Sshw1Q OX5WnBYpljzRoNrL8tAKQjSSMClyjcY+xw6w7pPS9yz+HRZimVD/AvAEoLmfzyRw6fOL jj4GX4S8NVznHlwOrUFCpzgxAXvqDTNR+gw+4Jqy4X2t/vPjOnlH8qobmcmSUJDT/y7j Wl/A== X-Gm-Message-State: ALoCoQmN2v3RfAc3HgLrRD0x0hmNwqqGcGRLqcRk0VgRzroBWqPFJLbU4Rg9SzPOvZbn9etH5LfM X-Received: by 10.180.105.74 with SMTP id gk10mr8242396wib.29.1432133121107; Wed, 20 May 2015 07:45:21 -0700 (PDT) Received: from xps13.localnet ([62.159.77.186]) by mx.google.com with ESMTPSA id gj7sm3849005wib.4.2015.05.20.07.45.19 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 20 May 2015 07:45:20 -0700 (PDT) From: Thomas Monjalon To: "Dumitrescu, Cristian" Date: Wed, 20 May 2015 16:44:35 +0200 Message-ID: <2017641.P0ts6fjbPO@xps13> Organization: 6WIND User-Agent: KMail/4.14.7 (Linux/4.0.1-1-ARCH; KDE/4.14.7; x86_64; ; ) In-Reply-To: <3EB4FA525960D640B5BDFFD6A3D891263236A65D@IRSMSX108.ger.corp.intel.com> References: <1430396143-10936-1-git-send-email-michalx.k.jastrzebski@intel.com> <43396928.Zqf8pLaHBD@xps13> <3EB4FA525960D640B5BDFFD6A3D891263236A65D@IRSMSX108.ger.corp.intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH v2] pipeline: add statistics for librte_pipeline ports and tables X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 20 May 2015 14:45:21 -0000 Please Cristian, do not top post. I'm replacing your comment in the right context. 2015-05-20 13:57, Dumitrescu, Cristian: > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com] > > Thanks for the detailed explanation. > > > > You are raising a trade-off problem about > > feature/maintenance/performance. > > I think we must choose among 4 solutions: > > 1/ always enabled > > 2/ build-time log level > > 3/ run-time option > > 4/ build-time option > > > > It's good to have this discussion and let other contributors giving their > > opinion. > > > > 2015-05-19 22:41, Dumitrescu, Cristian: > > > 1. What is the technical solution to avoid performance loss due to stats > > > support? > > > Generally, I would agree with you that config options should be avoided, > > > especially those that alter the API (function prototypes, data structure > > > layouts, etc). Please note this is not the case for any of our patches, > > > as only the stats collection is enabled/disabled, while the data > > > structures and functions are not changed by the build time option. > > > > > > But what can you do for statistics? We all know that collecting the stats > > > sucks up CPU cycles, especially due to memory accesses, so stats always > > > have a run-time cost. Traditionally, stats are typically enabled for > > > debugging purposes and then turned off for the release version when > > > performance is required. How can this be done if build time flags are not > > > used? > > > > Statistics in drivers are always enabled (first solution). > > If those statistics are only used for debugging, why not using the build-time > > option CONFIG_RTE_LOG_LEVEL? (second solution) > > Can you please describe what solution 2 on your list (build-time log > level) consists of? > > I see log level useful for printing messages when an event takes place, > but this is not what these stats patches are about. We want to poll > for those counters on demand: if the build-time flag is off, then the > value of those counters is 0; when the build-time is on, then the stats > counters have the real value. Basically, the build-time flag only > enables/disables the update of the counters at run-time, which is where > CPU cycles are consumed. I am not sure how the log levels can help here? I think that counting stats is a kind of logging. Some stats are always counted (see drivers) and you want to use these ones only for debugging (after rebuilding DPDK with some debug options). So I suggest, as second solution, to check CONFIG_RTE_LOG_LEVEL is at debug level instead of having one option per module. It would be implemented with "#if RTE_LOG_LEVEL == RTE_LOG_DEBUG" in RTE_PIPELINE_STATS_ADD.