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 at 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 > > - Panu - > > - Panu - >
