linux-kernel - Re: [PATCH bpf-next 2/3] tools: runqslower: build and use lightweight bootstrap version of bpftool

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Message-ID: <CAEf4BzYQM0RpsgUZgZpcMuDRSD2o96HzWzSeU5=GC0YfmjiXug@mail.gmail.com>
Date:   Wed, 13 Jul 2022 11:52:44 -0700
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Pu Lehui <pulehui@...wei.com>
Cc:     bpf <bpf@...r.kernel.org>, Networking <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Quentin Monnet <quentin@...valent.com>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>
Subject: Re: [PATCH bpf-next 2/3] tools: runqslower: build and use lightweight
 bootstrap version of bpftool

On Mon, Jul 11, 2022 at 7:37 PM Pu Lehui <pulehui@...wei.com> wrote:
>
> tools/runqslower use bpftool for vmlinux.h, skeleton, and static linking
> only. So we can use lightweight bootstrap version of bpftool to handle
> these, and it will be faster.
>
> Signed-off-by: Pu Lehui <pulehui@...wei.com>
> Suggested-by: Andrii Nakryiko <andrii@...nel.org>
> ---
>  tools/bpf/runqslower/Makefile | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/tools/bpf/runqslower/Makefile b/tools/bpf/runqslower/Makefile
> index da6de16a3dfb..8900c74f29e2 100644
> --- a/tools/bpf/runqslower/Makefile
> +++ b/tools/bpf/runqslower/Makefile
> @@ -4,7 +4,7 @@ include ../../scripts/Makefile.include
>  OUTPUT ?= $(abspath .output)/
>
>  BPFTOOL_OUTPUT := $(OUTPUT)bpftool/
> -DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)bpftool
> +DEFAULT_BPFTOOL := $(BPFTOOL_OUTPUT)bootstrap/bpftool
>  BPFTOOL ?= $(DEFAULT_BPFTOOL)
>  LIBBPF_SRC := $(abspath ../../lib/bpf)
>  BPFOBJ_OUTPUT := $(OUTPUT)libbpf/
> @@ -86,6 +86,12 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(BPFOBJ_OU
>         $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) OUTPUT=$(BPFOBJ_OUTPUT) \
>                     DESTDIR=$(BPFOBJ_OUTPUT) prefix= $(abspath $@) install_headers
>
> +ifeq ($(CROSS_COMPILE),)
>  $(DEFAULT_BPFTOOL): $(BPFOBJ) | $(BPFTOOL_OUTPUT)
>         $(Q)$(MAKE) $(submake_extras) -C ../bpftool OUTPUT=$(BPFTOOL_OUTPUT)   \
> -                   ARCH= CROSS_COMPILE= CC=$(HOSTCC) LD=$(HOSTLD)
> +                   LIBBPF_BOOTSTRAP_OUTPUT=$(BPFOBJ_OUTPUT)                   \
> +                   LIBBPF_BOOTSTRAP_DESTDIR=$(BPF_DESTDIR) bootstrap
> +else
> +$(DEFAULT_BPFTOOL): | $(BPFTOOL_OUTPUT)
> +       $(Q)$(MAKE) $(submake_extras) -C ../bpftool OUTPUT=$(BPFTOOL_OUTPUT) bootstrap
> +endif

Same comment as on the other patch, this CROSS_COMPILE if/else seems a
bit fragile, let's keep only the second cleaner part, maybe?


> --
> 2.25.1
>