Em qua., 10 de jan. de 2024 às 15:37, Ilya Maximets <[email protected]>
escreveu:
>
> On 1/9/24 13:53, Simon Horman wrote:
> > On Mon, Jan 08, 2024 at 08:34:36AM -0300, Roberto Bartzen Acosta via
dev wrote:
> >> Current version of debian/rules simply uses the default lto GCC
> >> optimization settings during the linkage process.
> >>
> >> The main problem with this approach is that GCC on OS like Ubuntu
> >> Jammy, for example, can enable the -flto=auto option during the
> >> openvswitch building and linking process. In this case, the linked
> >> dynamic libraries would need to be builded based on the same lto
> >> optimization options, at the risk of not working, according to
> >> documentation [1].
> >>
> >> I'm not sure of the real benefits of using this link-time optimization
>
> At least for DPDK-enabled builds LTO usually provides noticeable
> performance improvement. In the past I measured up to 10% packet
> rate increase with LTO. Though the gap went a bit lower with modern
> compilers. I think, it should still provide noticeable performance
> improvements at least for the userspace datapath.
>
> >> option, and since when it is enabled it causes problems with shared
> >> libs link libjemalloc, for example, it seems safer overwritten
> >> compiler decision by passing -fno-lto command.
>
> Building shared libraries with LTO is indeed a bit problematic.
> I agree that correctness should have a priority over potential
> performance benefits.
>
> Just out of curiosity, how do you add jemalloc into dependencies?
> Using one of the environment variables?
yeap, I'm just using the standard libs flag on a Ubuntu OS as suggested by
the OpenvSwitch documentation (*LIBS=-ljemalloc* ) [1]
override_dh_auto_configure: test -d _debian || mkdir _debian cd
_debian && ( \ test -e Makefile || \ ../configure
--prefix=/usr
--localstatedir=/var --enable-ssl LIBS=-ljemalloc \
--sysconfdir=/etc \
$(DATAPATH_CONFIGURE_OPTS) \
$(EXTRA_CONFIGURE_OPTS) \ )
[1] https://docs.openvswitch.org/en/latest/intro/install/general/
>
> >>
> >> [1] https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html#index-flto
> >>
> >> Reported-at:
https://bugs.launchpad.net/ubuntu/+source/openvswitch/+bug/2015748
> >> Signed-off-by: Roberto Bartzen Acosta <[email protected]>
> >
> > Hi,
> >
> > for one reason or another our automation was unable to apply this patch.
> > But I have done so locally in my own tree (it is not upstream)
> > and run the GitHub based tests with success:
> >
> > https://github.com/horms/ovs/actions/runs/7448358289
> >
> > From my point of view this patch seems reasonable.
> >
> > Acked-by: Simon Horman <[email protected]>
> >
> > But I would be interested to hear feedback from others before applying
it
> > to the upstream tree.
>
> @Frode, do you have any thoughts on this change? Is it a problem
> also for the main (in-distribution) Ubuntu/Debian builds?
>
> >
> >> ---
> >> debian/rules | 2 +-
> >> 1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/debian/rules b/debian/rules
> >> index dc5cc8a65..de8771813 100755
> >> --- a/debian/rules
> >> +++ b/debian/rules
> >> @@ -2,7 +2,7 @@
> >> # -*- makefile -*-
> >> #export DH_VERBOSE=1
> >> export DEB_BUILD_MAINT_OPTIONS = hardening=+all
> >> -export DEB_CFLAGS_MAINT_APPEND = -fPIC
> >> +export DEB_CFLAGS_MAINT_APPEND = -fPIC -fno-lto
>
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