[dpdk-dev] Forcing inlining for igb_uio and kni
Bruce Richardson
bruce.richardson at intel.com
Tue Jun 11 16:36:55 CEST 2019
On Tue, Jun 11, 2019 at 07:25:09AM -0700, Stephen Hemminger wrote:
> On Tue, 11 Jun 2019 11:18:22 +0100
> Bruce Richardson <bruce.richardson at intel.com> wrote:
>
> > On Tue, Jun 11, 2019 at 11:44:01AM +0200, David Marchand wrote:
> > > On Tue, Jun 11, 2019 at 11:31 AM Ilya Maximets
> > > <[1]i.maximets at samsung.com> wrote:
> > >
> > > On 11.06.2019 11:45, David Marchand wrote:
> > > > I noticed that OVS CI [1] patches the dpdk sources to force some
> > > inlining parameters and get kni and igb_uio to build fine.
> > > >
> > > > Looking at it in dpdk, meson support dropped this.
> > > > In the makefiles, I can't find a reason in the git history (we go
> > > back to 1.3.0rX version).
> > > >
> > > > [dmarchan at dmarchan dpdk]$ git grep max-inline-insns-single
> > > > kernel/linux/igb_uio/Makefile:MODULE_CFLAGS += -I$(SRCDIR) --param
> > > max-inline-insns-single=100
> > > > kernel/linux/kni/Makefile:MODULE_CFLAGS += -I$(SRCDIR) --param
> > > max-inline-insns-single=50
> > > > [dmarchan at dmarchan dpdk]$ git blame origin/master --
> > > kernel/linux/igb_uio/Makefile |grep max-inline-insns-single
> > > > 13dc56a6 lib/librte_eal/linuxapp/igb_uio/Makefile (Intel
> > > 2012-12-20 00:00:00 +0100 15) MODULE_CFLAGS += -I$(SRCDIR) --param
> > > max-inline-insns-single=100
> > > > [dmarchan at dmarchan dpdk]$ git blame origin/master --
> > > kernel/linux/kni/Makefile |grep max-inline-insns-single
> > > > 3fc5ca2f lib/librte_eal/linuxapp/kni/Makefile (Intel
> > > 2012-12-20 00:00:00 +0100 14) MODULE_CFLAGS += -I$(SRCDIR) --param
> > > max-inline-insns-single=50
> > > >
> > > > Is there a valid reason to keep this?
> > > > 1:
> > > [2]https://github.com/openvswitch/ovs/blob/master/.travis/linux-buil
> > > d.sh#L81
> > > <[3]https://protect2.fireeye.com/url?k=b7de159c45b1fa79.b7df9ed3-c48
> > > 06461f28ecaf5&u=https://github.com/openvswitch/ovs/blob/master/.trav
> > > is/linux-build.sh#L81>
> > > Hi, David.
> > > I don't know the reason for these in OVS travis config, But we don't
> > > need to know them, actually. I have a patch to drop all the kernel
> > > related stuff from the DPDK build in OVS Travis checks, just didn't
> > > send it yet. Will send soon, probably.
> > >
> > > I had this in mind since we don't need those kmods in the CI.
> > > Thanks Ilya.
> > > The question on dpdk side remains open :-).
> > > --
> > > David Marchand
> >
> > I know that previously we did have issues with the modules not compiling
> > due to errors about maximum levels of inlines. Whether that was because of
> > the compiler, or the kernel makefiles at the time, I'm not sure. The kmods
> > seem to build fine for me now without the parameters, and the fact that
> > there has never been a problem reported with building using meson either,
> > probably indicates that the extra compiler flags can be dropped.
> >
> > /Bruce
>
> I really doubt forcing inlining makes any difference to the performance.
I agree, especially for uio module. This was not a "perf" issue, but a
"just own't compile" issue, IIRC. :-)
That being said, given that this is just a line in two makefiles, the rule
about "if it ain't broke" may apply....
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