Den mån 21 jan. 2019 kl 20:12 skrev Jesper Dangaard Brouer <bro...@redhat.com>: > > On Mon, 21 Jan 2019 17:53:45 +0100 > Björn Töpel <bjorn.to...@gmail.com> wrote: > > > > If that jump tables are a common problem, I wonder, why the compiler > > > cannot be adapted to generate better performing code or an option passed > > > to the compiler. > > > > > > > It might make sense to use -fno-jump-tables or a better value for the > > case-values-threshold param for the i40e code. However, doing that > > would require a much broader testing, since there are a number of > > different places where a switch-statement is used. And depending on > > the context, a jump table might still be a better option. > > I recently found out that it is possible to disable GCC attributes per > function basis. See how I played with it here: > > https://github.com/xdp-project/xdp-project/blob/master/areas/dma/dma01_test_hellwig_direct_dma.org#investigate-overhead-of-bpf-indirect-retpoline >
Nice! ...but does that help here? I mean, excluding the thunks in jump table call generation isn't really an option? Is it possible in a function scoped way to change, say, the case-values-threshold? Björn > -- > Best regards, > Jesper Dangaard Brouer > MSc.CS, Principal Kernel Engineer at Red Hat > LinkedIn: http://www.linkedin.com/in/brouer
