Re: [PATCH bpf-next v3 7/7] tools/bpftool: Fix build slowdown

From: Andrii Nakryiko <andrii.nakryiko@gmail.com>
To: Jean-Philippe Brucker <jean-philippe@linaro.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>, bpf <bpf@vger.kernel.org>,
	Martin Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
	Yonghong Song <yhs@fb.com>, Andrii Nakryiko <andriin@fb.com>,
	john fastabend <john.fastabend@gmail.com>,
	KP Singh <kpsingh@chromium.org>
Subject: Re: [PATCH bpf-next v3 7/7] tools/bpftool: Fix build slowdown
Date: Tue, 10 Nov 2020 21:12:46 -0800	[thread overview]
Message-ID: <CAEf4BzbBmZFzyAsjY-rAr4_zX5Csjtfx4uxRoVjafBJAmCKN1Q@mail.gmail.com> (raw)
In-Reply-To: <20201110164310.2600671-8-jean-philippe@linaro.org>

On Tue, Nov 10, 2020 at 8:45 AM Jean-Philippe Brucker
<jean-philippe@linaro.org> wrote:
>
> Commit ba2fd563b740 ("tools/bpftool: Support passing BPFTOOL_VERSION to
> make") changed BPFTOOL_VERSION to a recursively expanded variable,
> forcing it to be recomputed on every expansion of CFLAGS and
> dramatically slowing down the bpftool build. Restore BPFTOOL_VERSION as
> a simply expanded variable, guarded by an ifeq().
>
> Fixes: ba2fd563b740 ("tools/bpftool: Support passing BPFTOOL_VERSION to make")
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> ---

Thanks a lot! I verified that it does restore the previous build speed.

Acked-by: Andrii Nakryiko <andrii@kernel.org>

> v3: new
> ---
>  tools/bpf/bpftool/Makefile | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index d566bced135e..804ade95929f 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -30,7 +30,9 @@ LIBBPF = $(LIBBPF_PATH)libbpf.a
>  LIBBPF_BOOTSTRAP_OUTPUT = $(BOOTSTRAP_OUTPUT)libbpf/
>  LIBBPF_BOOTSTRAP = $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
>
> -BPFTOOL_VERSION ?= $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
> +ifeq ($(BPFTOOL_VERSION),)
> +BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
> +endif
>
>  $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT):
>         $(QUIET_MKDIR)mkdir -p $@
> --
> 2.29.1
>