From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx.bisdn.de (mx.bisdn.de [185.27.182.31]) by dpdk.org (Postfix) with ESMTP id 39BB5595A for ; Tue, 3 Mar 2015 15:39:29 +0100 (CET) Received: from [192.168.1.35] (11.Red-79-144-249.dynamicIP.rima-tde.net [79.144.249.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx.bisdn.de (Postfix) with ESMTPSA id 7D4E6A1754; Tue, 3 Mar 2015 15:39:28 +0100 (CET) Message-ID: <54F5C79F.1090705@bisdn.de> Date: Tue, 03 Mar 2015 15:39:27 +0100 From: Marc Sune User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.4.0 MIME-Version: 1.0 To: "Ananyev, Konstantin" , "Richardson, Bruce" References: <1396546285-29972-1-git-send-email-cchemparathy@tilera.com> <2601191342CEEE43887BDE71AB9772580EF948F7@IRSMSX105.ger.corp.intel.com> <54E9C2C0.3090108@bisdn.de> <54F49E9D.6070201@bisdn.de> <20150303093355.GA7300@bricha3-MOBL3> <54F5A6CF.2090203@bisdn.de> <54F5ABCA.4010707@redhat.com> <54F5AF73.1060109@bisdn.de> <20150303130301.GA11084@bricha3-MOBL3> <2601191342CEEE43887BDE71AB977258213F38C9@irsmsx105.ger.corp.intel.com> In-Reply-To: <2601191342CEEE43887BDE71AB977258213F38C9@irsmsx105.ger.corp.intel.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH] mk: add support for gdb debug info generation 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: Tue, 03 Mar 2015 14:39:29 -0000 On 03/03/15 14:31, Ananyev, Konstantin wrote: > >> -----Original Message----- >> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Bruce Richardson >> Sent: Tuesday, March 03, 2015 1:03 PM >> To: Marc Sune >> Cc: dev@dpdk.org >> Subject: Re: [dpdk-dev] [PATCH] mk: add support for gdb debug info generation >> >> On Tue, Mar 03, 2015 at 01:56:19PM +0100, Marc Sune wrote: >>> On 03/03/15 13:40, Panu Matilainen wrote: >>>> On 03/03/2015 02:19 PM, Marc Sune wrote: >>>>> On 03/03/15 10:33, Bruce Richardson wrote: >>>>>> On Mon, Mar 02, 2015 at 06:32:13PM +0100, Marc Sune wrote: >>>>>>> On 22/02/15 12:51, Marc Sune wrote: >>>>>>>> I don't like the proposed patch, but I am recovering this old thread >>>>>>>> because I agree on the problem statement. >>>>>>>> >>>>>>>> On 04/04/14 11:57, Ananyev, Konstantin wrote: >>>>>>>>> Hi Cyril, >>>>>>>>> We already do have 'EXTRA_CFLAGS' and 'EXTRA_LDFLAGS' that you >>>>>>>>> can use >>>>>>>>> to enable debug, or any other compiler/linker options you need. >>>>>>>>> Wonder, why that is not enough? >>>>>>>> EXTRA_FLAGS var affects all the DPDK libraries. I was wondering why >>>>>>>> setting individually: >>>>>>>> >>>>>>>> diff --git a/config/common_linuxapp b/config/common_linuxapp >>>>>>>> index 2f9643b..04adc0d 100644 >>>>>>>> --- a/config/common_linuxapp >>>>>>>> +++ b/config/common_linuxapp >>>>>>>> @@ -127,7 +127,7 @@ CONFIG_RTE_LIBRTE_KVARGS=y >>>>>>>> # Compile generic ethernet library >>>>>>>> # >>>>>>>> CONFIG_RTE_LIBRTE_ETHER=y >>>>>>>> -CONFIG_RTE_LIBRTE_ETHDEV_DEBUG=n >>>>>>>> +CONFIG_RTE_LIBRTE_ETHDEV_DEBUG=y >>>>>>>> >>>>>>>> >>>>>>>> to put an example, does not set -g and -O0 in that particular module >>>>>>>> only. >>>>>>>> No one would ever use something compiled in DEBUG in production >>>>>>>> anyway. >>>>>>>> >>>>>>>> I always end up modifying manually Makefiles in the lib library that >>>>>>>> I am >>>>>>>> interested in having insides, overriding CFLAGS=-O3, which is not >>>>>>>> that >>>>>>>> nice. >>>>>>> I would like some feedback on this idea. If the community sees >>>>>>> benefit, I >>>>>>> will work on a patch for this. >>>>>>> >>>>>>> Marc >>>>>>> >>>>>> So, your proposal is to patch things so that any time one sets DEBUG=y >>>>>> in the >>>>>> build-time config for a library, we change the '-O3' to '-O0' and set >>>>>> -g also. >>>>>> Correct? >>>>> I am not sure what you mean by 'patch things'. I would simply enable the >>>>> build system to override the default compilation flags (now DPDK-wide, >>>>> or specifically librte_ wide) when _DEBUG=y for a library, changing >>>>> compilation flags from -O3 to -O0 -g and possibly also -fno-inline. I >>>>> have to check if -O0 already implicitly means -fno-inline (even for >>>>> __attribute__((always_inline)) ). >>>>> >>>>> I did a quick test. I chose KNI because it didn't have a DEBUG flag for >>>>> the user-space library. For other libraries, the existing _DEBUG setting >>>>> would be enough: >>>>> >>>>> marc@dpdk:~/dpdk$ git diff HEAD >>>>> diff --git a/config/common_linuxapp b/config/common_linuxapp >>>>> index 97f1c9e..8a3cef8 100644 >>>>> --- a/config/common_linuxapp >>>>> +++ b/config/common_linuxapp >>>>> @@ -405,6 +405,7 @@ CONFIG_RTE_LIBRTE_PIPELINE=y >>>>> # >>>>> CONFIG_RTE_LIBRTE_KNI=y >>>>> CONFIG_RTE_KNI_PREEMPT_DEFAULT=y >>>>> +CONFIG_RTE_LIBRTE_KNI_DEBUG=y >>>>> CONFIG_RTE_KNI_KO_DEBUG=n >>>>> CONFIG_RTE_KNI_VHOST=n >>>>> CONFIG_RTE_KNI_VHOST_MAX_CACHE_SIZE=1024 >>>>> diff --git a/lib/librte_kni/Makefile b/lib/librte_kni/Makefile >>>>> index 7107832..895f64e 100644 >>>>> --- a/lib/librte_kni/Makefile >>>>> +++ b/lib/librte_kni/Makefile >>>>> @@ -34,7 +34,7 @@ include $(RTE_SDK)/mk/rte.vars.mk >>>>> # library name >>>>> LIB = librte_kni.a >>>>> >>>>> -CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR) -O3 -fno-strict-aliasing >>>>> +CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR) $(CONFIG_RTE_LIBRTE_KNI_CFLAGS) >>>>> >>>>> EXPORT_MAP := rte_kni_version.map >>>>> >>>>> diff --git a/mk/rte.app.mk b/mk/rte.app.mk >>>>> index 63a41e2..eee477d 100644 >>>>> --- a/mk/rte.app.mk >>>>> +++ b/mk/rte.app.mk >>>>> @@ -78,6 +78,13 @@ endif >>>>> ifeq ($(CONFIG_RTE_LIBRTE_KNI),y) >>>>> ifeq ($(CONFIG_RTE_EXEC_ENV_LINUXAPP),y) >>>>> LDLIBS += -lrte_kni >>>>> + >>>>> +ifeq ($(CONFIG_RTE_LIBRTE_KNI_DEBUG),y) >>>>> +CONFIG_RTE_LIBRTE_KNI_CFLAGS = -O0 -g -fno-strict-aliasing -fno-inline >>>>> +else >>>>> +CONFIG_RTE_LIBRTE_KNI_CFLAGS = -O3 -fno-strict-aliasing >>>>> +endif >>>>> + >>>>> endif >>>>> endif >>>>> >>>>> >>>>> Thoughts? >>>> My 5c is that if anything, DPDK needs *less* places that muck around with >>>> compiler flags, not more. If you something like this for all the libraries >>>> in DPDK the number doesn't just increase a bit, it explodes. >>> If you check the part below this one in my original email, that you stripped >>> out (without notice), the suggestion was also to add a global _DEBUG >>> parameter for the entire DPDK set of libraries, to change all the CFLAGS at >>> once (not in the attached PATCH). >>> >>>> I dont see that much point in this thing, but I'd approach it by defining >>>> the debug flags someplace central, say DEBUG_FLAGS, and append that to the >>>> common cflags when *_DEBUG config is enabled. At least with gcc the last >>>> option wins so if you just append -O0 when debugging then that's what >>>> wins, the earlier -O3 does not matter. >>> The original problem is the one you expose; libraries hardcode the CFLAGS, >>> ignoring user-flags. There is no way to change this unless you change the >>> Makefiles directly. >>> >>> But right now, each library does hardcode its *own* flags (check Makefiles >>> for the libraries), so there is already not a unified approach here. I see >>> for instance KNI having -fno-strict-aliasing while other libraries don't. >>> >>> Having said that, there are moments, specially with -O3, in which to be able >>> to reproduce a bug, you need to compile certain parts of code with -O3 and >>> the rest with -O0 -g (the ones to be debugged). The approach proposed (both >>> a global *and* a lib specific) allows that. >>> >>> Marc >>> >> I believe that the global option of overriding the CFLAGS is already sufficiently >> covered - including being documented in programmers guide - by EXTRA_CFLAGS. The >> ability to turn off optimization support for a single library is not covered >> anywhere, and that suggestion seems reasonable to me. For each library, we can >> just append '-O0 -g' to the CFLAGS in that libraries makefile if the debug option >> is set. I don't see that as significantly complicating things [though I wouldn't >> make any changes to the rte.app.mk to allow this, just have it per lib in the >> lib's makefile] >> > Well, but then people would say 'why only -g -O0' for _DEBUG config option? > And would ask for ability to add/change other compile options to add/change for particular library. > If we need that, probably we can introduce RTE_LIBRTE__EXTRA_CFLAGS config macros for each library? > So people can set them in their config files to whatever they like? It is not a bad idea either. However, there are already those _DEBUG config elements (the KNI is a special case). Maybe both can be combined (i.e. RTE_LIBRTE__EXTRA_CFLAGS should always override _DEBUG). It would probably get a bit over-engineered then, though. marc > > Konstantin