Re: [dpdk-dev] [PATCH v2 1/4] mk: Remove combined library and related options

["Kavanagh, Mark B" <mark.b.kavanagh@intel.com>]

>-----Original Message-----
>From: Gonzalez Monroy, Sergio
>Sent: Friday, March 13, 2015 11:49 AM
>To: Kavanagh, Mark B
>Cc: dev@dpdk.org
>Subject: Re: [dpdk-dev] [PATCH v2 1/4] mk: Remove combined library and related options
>
>On 13/03/2015 11:34, Kavanagh, Mark B wrote:
>>> On 13/03/2015 10:49, Kavanagh, Mark B wrote:
>>>>> ---
>>>>> config/common_bsdapp                        |   6 --
>>>>> config/common_linuxapp                      |   6 --
>>>>> config/defconfig_ppc_64-power8-linuxapp-gcc |   2 -
>>>>> lib/Makefile                                |   1 -
>>>>> mk/rte.app.mk                               |  12 ----
>>>>> mk/rte.lib.mk                               |  35 ----------
>>>>> mk/rte.sdkbuild.mk                          |   3 -
>>>>> mk/rte.sharelib.mk                          | 101 ----------------------------
>>>>> mk/rte.vars.mk                              |   9 ---
>>>>> 9 files changed, 175 deletions(-)
>>>>> delete mode 100644 mk/rte.sharelib.mk
>>>>>
>>>>> diff --git a/config/common_bsdapp b/config/common_bsdapp
>>>>> index 8ff4dc2..7ee5ecf 100644
>>>>> --- a/config/common_bsdapp
>>>>> +++ b/config/common_bsdapp
>>>>> @@ -79,12 +79,6 @@ CONFIG_RTE_FORCE_INTRINSICS=n
>>>>> CONFIG_RTE_BUILD_SHARED_LIB=n
>>>>>
>>>>> #
>>>>> -# Combine to one single library
>>>>> -#
>>>>> -CONFIG_RTE_BUILD_COMBINE_LIBS=n
>>>>> -CONFIG_RTE_LIBNAME=intel_dpdk
>>>> Hi Sergio,
>>>>
>>>> Removing these options breaks compatibility with OVS. While it may be feasible to link
>>> to individual static libraries, in our experience, a single combined library provides a
>>> much more convenient way of linking.
>>>> Thanks,
>>>> Mark
>>>>
>>>>> -
>>
>> (snip)
>>
>>
>>>>> -endif
>>>>> -
>>>>> -RTE_LIBNAME := $(CONFIG_RTE_LIBNAME:"%"=%)
>>>>> -ifeq ($(RTE_LIBNAME),)
>>>>> -RTE_LIBNAME := intel_dpdk
>>>>> endif
>>>>>
>>>>> # RTE_TARGET is deducted from config when we are building the SDK.
>>>>> --
>>>>> 1.9.3
>>> Hi Mark,
>>>
>>> How does this patch break compatibility with OVS?
>>>
>>> Thanks,
>>> Sergio
>> Hey Sergio,
>>
>> We use the CONFIG_RTE_BUILD_COMBINE_LIBS and CONFIG_RTE_LINBNAME flags to build a single
>static DPDK library, named 'libintel_dpdk.a', which OVS links against. Removing the
>combined library option breaks compatibility with any application that links against the
>combined DPDK library.
>>
>> Is there a strong technical motivation for removing these options?
>>
>> Thanks,
>> Mark
> From a shared library point of view, it just does not make sense to
>have applications linked against a 'combined' library that may have
>different features built in it.
>

For OVS, we don't build DPDK as a set of shared libraries, but rather an individual static library, due to the performance penalties inherent in using shared libraries.

>Removing these options, aside from the obvious 'less build config
>option', it simplifies maintenance of makefiles as we currently have a
>separated makefile with specific rules just for combined library.
>
>It is pretty straight forward to build a single combined archive out of
>multiple archives, would it be acceptable to have a script to do this?
>

This seems a bit 'hacky' to me and I'm not sure that it would be amenable to the OVS maintainers. Unless I'm overlooking something here, I'd prefer to maintain the status quo.

>Thanks,
>Sergio