[Intel-wired-lan] [PATCH] i40e: replace switch-statement with if-clause
Jesper Dangaard Brouer
brouer at redhat.com
Mon Jan 21 19:12:13 UTC 2019
On Mon, 21 Jan 2019 17:53:45 +0100
Björn Töpel <bjorn.topel at 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
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
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