netdev - Re: [PATCH bpf-next 2/3] libbpf/tools: add runqslower tool to libbpf

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Message-ID: <CAEf4BzYFwJiKdTfXvSjcygOSySUqavFY3zaHZ4-0wcSkvHXRdw@mail.gmail.com>
Date:   Thu, 19 Dec 2019 13:16:27 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Andrii Nakryiko <andriin@...com>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Alexei Starovoitov <ast@...com>,
        "daniel@...earbox.net" <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH bpf-next 2/3] libbpf/tools: add runqslower tool to libbpf

On Thu, Dec 19, 2019 at 10:13 AM Yonghong Song <yhs@...com> wrote:
>
>
>
> On 12/18/19 11:06 PM, Andrii Nakryiko wrote:
> > Convert one of BCC tools (runqslower [0]) to BPF CO-RE + libbpf. It matches
> > its BCC-based counterpart 1-to-1, supporting all the same parameters and
> > functionality.
> >
> > runqslower tool utilizes BPF skeleton, auto-generated from BPF object file,
> > as well as memory-mapped interface to global (read-only, in this case) data.
> > Its makefile also ensures auto-generation of "relocatable" vmlinux.h, which is
> > necessary for BTF-typed raw tracepoints with direct memory access.
> >
> >    [0] https://github.com/iovisor/bcc/blob/11bf5d02c895df9646c117c713082eb192825293/tools/runqslower.py
> >
> > Signed-off-by: Andrii Nakryiko <andriin@...com>
> > ---
> >   tools/lib/bpf/tools/runqslower/.gitignore     |   2 +
> >   tools/lib/bpf/tools/runqslower/Makefile       |  60 ++++++
> >   .../lib/bpf/tools/runqslower/runqslower.bpf.c | 101 ++++++++++
> >   tools/lib/bpf/tools/runqslower/runqslower.c   | 187 ++++++++++++++++++
> >   tools/lib/bpf/tools/runqslower/runqslower.h   |  13 ++
> >   5 files changed, 363 insertions(+)
> >   create mode 100644 tools/lib/bpf/tools/runqslower/.gitignore
> >   create mode 100644 tools/lib/bpf/tools/runqslower/Makefile
> >   create mode 100644 tools/lib/bpf/tools/runqslower/runqslower.bpf.c
> >   create mode 100644 tools/lib/bpf/tools/runqslower/runqslower.c
> >   create mode 100644 tools/lib/bpf/tools/runqslower/runqslower.h
> >
> > diff --git a/tools/lib/bpf/tools/runqslower/.gitignore b/tools/lib/bpf/tools/runqslower/.gitignore
> > new file mode 100644
> > index 000000000000..404942cc9371
> > --- /dev/null
> > +++ b/tools/lib/bpf/tools/runqslower/.gitignore
> > @@ -0,0 +1,2 @@
> > +/.output
> > +/runqslower
> > diff --git a/tools/lib/bpf/tools/runqslower/Makefile b/tools/lib/bpf/tools/runqslower/Makefile
> > new file mode 100644
> > index 000000000000..b87b1f9fe9da
> > --- /dev/null
> > +++ b/tools/lib/bpf/tools/runqslower/Makefile
> > @@ -0,0 +1,60 @@
> > +# SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)
> > +CLANG := clang
> > +LLC := llc
> > +LLVM_STRIP := llvm-strip
> > +BPFTOOL := bpftool
>
> Maybe it is better to use in-tree bpftool? This will ensure we use the
> one shipped together with the source which should have needed functionality.

I can do that as well, though I tried to keep it close enough to how
libbpf+CO-RE applications are going to be built in the wild, so tried
to minimize amount of in-kernel source tree assumptions. Ideally both
bpftool is installed and libbpf is available as a dynamic library in
the system. But surely I can add bpftool auto-build and use that one.

>
> > +LIBBPF_SRC := ../..
> > +CFLAGS := -g -Wall
> > +
> > +# Try to detect best kernel BTF source
> > +KERNEL_REL := $(shell uname -r)
> > +ifneq ("$(wildcard /sys/kenerl/btf/vmlinux)","")
> > +VMLINUX_BTF := /sys/kernel/btf/vmlinux
> > +else ifneq ("$(wildcard /boot/vmlinux-$(KERNEL_REL))","")
> > +VMLINUX_BTF := /boot/vmlinux-$(KERNEL_REL)
> > +else
> > +$(error "Can't detect kernel BTF, use VMLINUX_BTF to specify it explicitly")
> > +endif
> > +
> > +out := .output
> > +abs_out := $(abspath $(out))
> > +libbpf_src := $(abspath $(LIBBPF_SRC))
> > +
> > +.DELETE_ON_ERROR:
> > +
> > +.PHONY: all
> > +all: runqslower
> > +
> > +.PHONY: clean
> > +clean:
> > +     rm -rf $(out) runqslower
> > +
> > +runqslower: $(out)/runqslower.o $(out)/libbpf.a
> > +     $(CC) $(CFLAGS) -lelf -lz $^ -o $@
> > +
> > +$(out)/vmlinux.h: $(VMLINUX_BTF) | $(out)
> > +     $(BPFTOOL) btf dump file $(VMLINUX_BTF) format core > $@
> > +
> > +$(out)/libbpf.a: | $(out)
> > +     cd $(out) &&                                                          \
> > +     $(MAKE) -C $(libbpf_src) OUTPUT=$(abs_out)/ $(abs_out)/libbpf.a
> > +
> > +$(out)/runqslower.o: runqslower.h $(out)/runqslower.skel.h                 \
> > +                  $(out)/runqslower.bpf.o
> > +
> > +$(out)/runqslower.bpf.o: $(out)/vmlinux.h runqslower.h
> > +
> > +$(out)/%.skel.h: $(out)/%.bpf.o
> > +     $(BPFTOOL) gen skeleton $< > $@
> > +
> > +$(out)/%.bpf.o: %.bpf.c | $(out)
> > +     $(CLANG) -g -O2 -target bpf -I$(out) -I$(LIBBPF_SRC)                  \
> > +              -c $(filter %.c,$^) -o $@ &&                                 \
> > +     $(LLVM_STRIP) -g $@
> > +
> > +$(out)/%.o: %.c | $(out)
> > +     $(CC) $(CFLAGS) -I$(LIBBPF_SRC) -I$(out) -c $(filter %.c,$^) -o $@
> > +
> > +$(out):
> > +     mkdir -p $(out)
> > +
> [...]