netdev - Re: [PATCH bpf-next 3/3] selftests/bpf: add pyperf scale test

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Date:   Tue, 21 May 2019 17:56:02 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Alexei Starovoitov <ast@...com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Networking <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH bpf-next 3/3] selftests/bpf: add pyperf scale test

On Tue, May 21, 2019 at 5:50 PM Alexei Starovoitov <ast@...com> wrote:
>
> On 5/21/19 5:36 PM, Andrii Nakryiko wrote:
> >> --- /dev/null
> >> +++ b/tools/testing/selftests/bpf/progs/pyperf.h
> >> @@ -0,0 +1,268 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +// Copyright (c) 2019 Facebook
> >
> > Maybe let's include a link to an up-to-date real tool, that was used
> > to create this scale test in BCC:
> > https://github.com/iovisor/bcc/blob/master/examples/cpp/pyperf/PyPerfBPFProgram.cc
>
> I thought about it, but decided not to,
> since this hack is not exactly the same.
> I tried to keep an idea of the loop though
> with roughly the same number of probe_reads
> and 'if' conditions, but was chopping all bcc-ism out of it.
> In the commit log: "Add a snippet of pyperf bpf program"
> By "a snippet" I meant that it's not the same thing,
> but close enough from verifier complexity point of view.
> Existing pyperf works around the lack of loops with tail-calls :(
> I'm thinking to reuse this hack as future bounded loop test too.
>
> Another reason to avoid the link is I'm hoping that pyperf
> will move from 'examples' directory there into proper tool,
> so the link will become broken.

Ok, fair enough.