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

[Neil Horman <nhorman@tuxdriver.com>]

On Fri, Mar 13, 2015 at 04:12:35PM +0200, Stefan Puiu wrote:
> Hi,
> 
> 2 cents from a DPDK library user - I make 2 changes to the default
> linux+gcc configuration: combine libraries and build shared libraries
> (since I want 2 instances of the app, it didn't make sense to me to
> link statically). I tried working with the individual libs, but adding
> all of them with --start-group/-end-group just seemed so much more
> painful than simply linking against one lib. I know there are some
> Makefile variables to help with this, but I use scons for building my
> app, so that doesn't help much.
> 
> Of course, if that can be achieved easily after building all the
> libraries, that's fine. But I think combining the libs makes a lot of
> sense in many cases.
> 
So do it, create a linker script that internally contains one line:
INPUT(-lrte_eal -lrte_alarm -lrte_mempool ... etc)

Name the file libdpdk.so

then when you build your app, just link -ldpdk

Done.

Neil

> Thanks,
> Stefan.
> 
> On Fri, Mar 13, 2015 at 3:17 PM, Neil Horman <nhorman@tuxdriver.com> wrote:
> > On Fri, Mar 13, 2015 at 11:48:59AM +0000, Gonzalez Monroy, Sergio wrote:
> >> 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.
> >>
> >> 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?
> >>
> >> Thanks,
> >> Sergio
> >>
> > +1
> >
> > For the static case, its easy to do a post build combination of archives.  For
> > the shared library case, its equally easy to simply create a linker scripts call
> > <CONFIG_RTE_LIBNAME>.so that pulls in all the individual libraries.
> >
> > Neil
> >
>