On Tue, 10 Dec 2019 at 12:05, Jesper Dangaard Brouer <brouer@xxxxxxxxxx> wrote:
>
> On Mon, 9 Dec 2019 14:55:21 +0100
> Björn Töpel <bjorn.topel@xxxxxxxxx> wrote:
>
> > From: Björn Töpel <bjorn.topel@xxxxxxxxx>
> >
> > The xdp_perf is a dummy XDP test, only used to measure the the cost of
> > jumping into a XDP program.
>
> I really like this idea of performance measuring XDP-core in isolation.
> This is the ultimate zoom-in micro-benchmarking. I see a use-case for
> this, where I will measure the XDP-core first, and then run same XDP
> prog (e.g. XDP_DROP) on a NIC driver, then I can deduct/isolate the
> driver-code and hardware overhead. We/I can also use it to optimize
> e.g. REDIRECT code-core (although redir might not actually work).
>
> IMHO it would be valuable to have bpf_prog_load() also measure the
> perf-HW counters for 'cycles' and 'instructions', as in your case the
> performance optimization was to improve the instructions-per-cycle
> (which you showed via perf stat in cover letter).
>
>
> If you send a V4 please describe how to use this prog to measure the
> cost, as you describe in cover letter.
>
> from selftests/bpf run:
> # test_progs -v -t xdp_perf
>
> (This is a nitpick, so only do this if something request a V4)
>
I'll definitely do a v4! Thanks for the input/comments! I'll address
them in the next rev!
Cheers,
Björn
>
> > Signed-off-by: Björn Töpel <bjorn.topel@xxxxxxxxx>
> > ---
> > .../selftests/bpf/prog_tests/xdp_perf.c | 25 +++++++++++++++++++
> > 1 file changed, 25 insertions(+)
> > create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_perf.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_perf.c b/tools/testing/selftests/bpf/prog_tests/xdp_perf.c
> > new file mode 100644
> > index 000000000000..7185bee16fe4
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/xdp_perf.c
> > @@ -0,0 +1,25 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include <test_progs.h>
> > +
> > +void test_xdp_perf(void)
> > +{
> > + const char *file = "./xdp_dummy.o";
> > + __u32 duration, retval, size;
> > + struct bpf_object *obj;
> > + char in[128], out[128];
> > + int err, prog_fd;
> > +
> > + err = bpf_prog_load(file, BPF_PROG_TYPE_XDP, &obj, &prog_fd);
> > + if (CHECK_FAIL(err))
> > + return;
> > +
> > + err = bpf_prog_test_run(prog_fd, 1000000, &in[0], 128,
> > + out, &size, &retval, &duration);
> > +
> > + CHECK(err || retval != XDP_PASS || size != 128,
> > + "xdp-perf",
> > + "err %d errno %d retval %d size %d\n",
> > + err, errno, retval, size);
> > +
> > + bpf_object__close(obj);
> > +}
>
>
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
