Re: ANNOUNCE: pahole v1.22 (Multithreaded DWARF Loading, detached BTF encoding)

Arnaldo Carvalho de Melo
2021-08-23T21:56:01Z

Em Mon, Aug 23, 2021 at 06:25:57PM -0300, Arnaldo Carvalho de Melo escreveu:
> Hi,
>
> The v1.22 release of pahole and its friends is out, this time
> the main new features are the ability to encode BTF to a
> separate file and Multithreaded DWARF loading.
>
> Lots of cleanups and improvements resulted from preparing for
> multithreading. Please see the changes-1.22 file in the source tree and
> at the end of this message for a detailed list of improvements.
>
> Next step is to multithread BTF encoding, but even without that
> the time taken tp encode the kernel BTF information now is slashed by
> over 50%. The before/after 'perf stat' output for each of the improvements
> can be found in the project git commit log messages.
>
> The non-cross build set of containers used to test build the
> Linux perf tools is now being used to make sure pahole doesn't build
> regresses.
>
> Thanks as well to Andrii for putting in place a CI job for pahole
> at https://github.com/libbpf/libbpf/actions/workflows/pahole.yml.
>
> Main git repo:
>
> git://git.kernel.org/pub/scm/devel/pahole/pahole.git
>
> Mirror git repo:
>
> https://github.com/acmel/dwarves.git
>
> tarball + gpg signature:
>
> https://fedorapeople.org/~acme/dwarves/dwarves-1.21.tar.xz
> https://fedorapeople.org/~acme/dwarves/dwarves-1.21.tar.bz2
> https://fedorapeople.org/~acme/dwarves/dwarves-1.21.tar.sign

Oh well, really at:

https://fedorapeople.org/~acme/dwarves/dwarves-1.22.tar.xz
https://fedorapeople.org/~acme/dwarves/dwarves-1.22.tar.bz2
https://fedorapeople.org/~acme/dwarves/dwarves-1.22.tar.sign

:-)

> Thanks a lot to all the contributors and distro packagers, you're on the
> CC list, I appreciate a lot the work you put into these tools,
>
> Best Regards,
>
> - Arnaldo
>
> pahole:
>
> - Allow encoding BTF to a separate BTF file (detached) instead of to a new
> ".BTF" ELF section in the file being encoded (vmlinux usually).
>
> - Introduce -j/--jobs option to specify the number of threads to use. Without
> arguments means one thread per CPU. So far used for the DWARF loader, will
> be used as well for the BTF encoder.
>
> - Show all different types with the same name, not just the first one found.
>
> - Introduce sorted type output (--sort), needed with multithreaded DWARF loading,
> to use with things like 'btfdiff' that expects the output from DWARF and BTF
> types to be comparable using 'diff'.
>
> - Stop assuming that reading from stdin means pretty printing as this broke
> pre-existing scripts, introduce a explicit --prettify command line option.
>
> - Improve type resolution for the --header command line option.
>
> - Disable incomplete CTF encoder, this needs to be done using the external
> libctf library.
>
> - Do not consider the ftrace filter when encoding BTF for kernel functions.
>
> - Add --kabi_prefix to avoid deduplication woes when using _RH_KABI_REPLACE(),
>
> - Add --with_flexible_array to show just types with flexible arrays.
>
> DWARF Loader:
>
> - Multithreaded loading, requires elfutils >= 0.178.
>
> - Lock calls to non-thread safe elfutils' libdw functions (dwarf_decl_file()
> and dwarf_decl_line())
>
> - Change hash table size to one that performs better with current typical
> vmlinux files.
>
> - Allow tweaking the hash table size from the command line.
>
> - Stop allocating memory for strings obtained from libdw, just defer freeing
> the Dwfl handler so that references to its strings can be safely kept.
>
> - Use a frontend cache for the latest lookup result.
>
> - Allow ignoring some DWARF tags when loading for encoding BTF, as BTF doesn't
> have equivalents for things like DW_TAG_inline_expansion and DW_TAG_label.
>
> - Allow ignoring some DWARF tag attributes, such as DW_AT_alignment, not used
> when encoding BTF.
>
> - Do not query for non-C attributes when loading a C language CU (compilation unit).
>
> BTF encoder:
>
> - Preparatory work for multithreaded encoding, the focus for 1.23.
>
> btfdiff:
>
> - Support diffing against a detached BTF file, e.g.: 'btfdiff vmlinux vmlinux.btf'
>
> - Support multithreaded DWARF loading, using the new pahole --sort option to have
> the output from both BTF and DWARF sorted and thus comparable via 'diff'.
>
> Build:
>
> - Support building with libc libraries lacking either obstacks or argp, such
> as Alpine Linux's musl libc.
>
> - Support systems without getconf() to obtain the data cacheline size, such
> as musl libc.
>
> - Add a buildcmd.sh for test builds, tested using the same set of containers
> used for testing the Linux kernel perf tools.
>
> - Enable selecting building with a shared libdwarves library or statically.
>
> - Allow to use the libbpf package found in distributions instead of with the
> accompanying libbpf git submodule.
>
> Cleanups:
>
> - Address lots of compiler warnings accumulated by not using -Wextra, it'll
> be added in the next release after allowing not to use it to build libbpf.
>
> - Address covscan report issues.
>
> Documentation:
>
> - Improve the --nr_methods/-m pahole man page entry.
>
> - Clarify that currently --nr_methods doesn't work together witn -C.
>
> Tests:
>
> $ export BUILD_TARBALL=http://192.168.100.2/pahole/dwarves-1.22.tar.xz
> $ export BUILD_CMD=buildcmd.sh
> $ time dm -X
> 1 3.78 almalinux:8 : Ok gcc (GCC) 8.4.1 20200928 (Red Hat 8.4.1-1) , clang version 11.0.0 (Red Hat 11.0.0-1.module_el8.4.0+2107+39fed697)
> 2 5.07 alpine:3.12 : Ok gcc (Alpine 9.3.0) 9.3.0 , Alpine clang version 10.0.0 (https://gitlab.alpinelinux.org/alpine/aports.git 7445adce501f8473efdb93b17b5eaf2f1445ed4c)
> 3 5.48 alpine:3.13 : Ok gcc (Alpine 10.2.1_pre1) 10.2.1 20201203 , Alpine clang version 10.0.1
> 4 5.68 alpine:3.14 : Ok gcc (Alpine 10.3.1_git20210424) 10.3.1 20210424 , Alpine clang version 11.1.0
> 5 5.99 alpine:edge : Ok gcc (Alpine 10.3.1_git20210625) 10.3.1 20210625 , Alpine clang version 11.1.0
> 6 4.27 alt:p8 : Ok x86_64-alt-linux-gcc (GCC) 5.3.1 20151207 (ALT p8 5.3.1-alt3.M80P.1) , clang version 3.8.0 (tags/RELEASE_380/final)
> 7 4.27 alt:p9 : Ok x86_64-alt-linux-gcc (GCC) 8.4.1 20200305 (ALT p9 8.4.1-alt0.p9.1) , clang version 10.0.0
> 8 5.07 alt:sisyphus : Ok x86_64-alt-linux-gcc (GCC) 10.2.1 20210313 (ALT Sisyphus 10.2.1-alt3) , clang version 10.0.1
> 9 4.67 amazonlinux:1 : Ok gcc (GCC) 7.2.1 20170915 (Red Hat 7.2.1-2) , clang version 3.6.2 (tags/RELEASE_362/final)
> 10 4.27 amazonlinux:2 : Ok gcc (GCC) 7.3.1 20180712 (Red Hat 7.3.1-13) , clang version 11.1.0 (Amazon Linux 2 11.1.0-1.amzn2.0.2)
> 11 4.48 centos:8 : Ok gcc (GCC) 8.4.1 20200928 (Red Hat 8.4.1-1) , clang version 11.0.0 (Red Hat 11.0.0-1.module_el8.4.0+587+5187cac0)
> 12 4.48 centos:stream : Ok gcc (GCC) 8.5.0 20210514 (Red Hat 8.5.0-3) , clang version 12.0.0 (Red Hat 12.0.0-1.module_el8.5.0+840+21214faf)
> 13 4.18 clearlinux:latest : Ok gcc (Clear Linux OS for Intel Architecture) 11.2.1 20210816 releases/gcc-11.2.0-71-g4a414ac2a5 , clang version 11.1.0
> 14 4.88 debian:9 : Ok gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516 , clang version 3.8.1-24 (tags/RELEASE_381/final)
> 15 4.79 debian:10 : Ok gcc (Debian 8.3.0-6) 8.3.0 , clang version 7.0.1-8+deb10u2 (tags/RELEASE_701/final)
> 16 4.18 debian:11 : Ok gcc (Debian 10.2.1-6) 10.2.1 20210110 , Debian clang version 11.0.1-2
> 17 4.27 debian:experimental : Ok gcc (Debian 10.2.1-6) 10.2.1 20210110 , Debian clang version 11.0.1-2
> 18 3.77 fedora:22 : Ok gcc (GCC) 5.3.1 20160406 (Red Hat 5.3.1-6) , clang version 3.5.0 (tags/RELEASE_350/final)
> 19 3.97 fedora:23 : Ok gcc (GCC) 5.3.1 20160406 (Red Hat 5.3.1-6) , clang version 3.7.0 (tags/RELEASE_370/final)
> 20 4.17 fedora:24 : Ok gcc (GCC) 6.3.1 20161221 (Red Hat 6.3.1-1) , clang version 3.8.1 (tags/RELEASE_381/final)
> 21 4.37 fedora:25 : Ok gcc (GCC) 6.4.1 20170727 (Red Hat 6.4.1-1) , clang version 3.9.1 (tags/RELEASE_391/final)
> 22 4.48 fedora:26 : Ok gcc (GCC) 7.3.1 20180130 (Red Hat 7.3.1-2) , clang version 4.0.1 (tags/RELEASE_401/final)
> 23 4.28 fedora:27 : Ok gcc (GCC) 7.3.1 20180712 (Red Hat 7.3.1-6) , clang version 5.0.2 (tags/RELEASE_502/final)
> 24 4.47 fedora:28 : Ok gcc (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2) , clang version 6.0.1 (tags/RELEASE_601/final)
> 25 4.37 fedora:29 : Ok gcc (GCC) 8.3.1 20190223 (Red Hat 8.3.1-2) , clang version 7.0.1 (Fedora 7.0.1-6.fc29)
> 26 4.28 fedora:30 : Ok gcc (GCC) 9.3.1 20200408 (Red Hat 9.3.1-2) , clang version 8.0.0 (Fedora 8.0.0-3.fc30)
> 27 4.07 fedora:31 : Ok gcc (GCC) 9.3.1 20200408 (Red Hat 9.3.1-2) , clang version 9.0.1 (Fedora 9.0.1-4.fc31)
> 28 4.27 fedora:32 : Ok gcc (GCC) 10.3.1 20210422 (Red Hat 10.3.1-1) , clang version 10.0.1 (Fedora 10.0.1-3.fc32)
> 29 4.38 fedora:33 : Ok gcc (GCC) 10.3.1 20210422 (Red Hat 10.3.1-1) , clang version 11.0.0 (Fedora 11.0.0-3.fc33)
> 30 4.47 fedora:34 : Ok gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1) , clang version 12.0.1 (Fedora 12.0.1-1.fc34)
> 31 4.37 fedora:35 : Ok gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1) , clang version 13.0.0 (Fedora 13.0.0~rc1-1.fc35)
> 32 4.37 fedora:rawhide : Ok gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1) , clang version 12.0.1 (Fedora 12.0.1-2.fc35)
> 33 4.08 gentoo-stage3:latest : Ok gcc (Gentoo 10.3.0 p1) 10.3.0
> 34 4.07 mageia:6 : Ok gcc (Mageia 5.5.0-1.mga6) 5.5.0 , clang version 3.9.1 (tags/RELEASE_391/final)
> 35 4.78 mageia:7 : Ok gcc (Mageia 8.4.0-1.mga7) 8.4.0 , clang version 8.0.0 (Mageia 8.0.0-1.mga7)
> 36 6.48 openmandriva:cooker : Ok gcc (GCC) 11.2.0 20210728 (OpenMandriva) , OpenMandriva 12.0.1-1 clang version 12.0.1 (/builddir/build/BUILD/llvm-project-12.0.1.src/clang 0a7362bac93d0a3bf152ead1b6b3f98c9a9695d5)
> 37 4.48 opensuse:15.0 : Ok gcc (SUSE Linux) 7.4.1 20190905 [gcc-7-branch revision 275407] , clang version 5.0.1 (tags/RELEASE_501/final 312548)
> 38 4.08 opensuse:15.1 : Ok gcc (SUSE Linux) 7.5.0 , clang version 7.0.1 (tags/RELEASE_701/final 349238)
> 39 3.87 opensuse:15.2 : Ok gcc (SUSE Linux) 7.5.0 , clang version 9.0.1
> 40 3.78 opensuse:15.3 : Ok gcc (SUSE Linux) 7.5.0 , clang version 11.0.1
> 41 4.38 opensuse:tumbleweed : Ok gcc (SUSE Linux) 11.1.1 20210721 [revision 076930b9690ac3564638636f6b13bbb6bc608aea] , clang version 12.0.1
> 42 3.87 oraclelinux:8 : Ok gcc (GCC) 8.4.1 20200928 (Red Hat 8.4.1-1.0.1) , clang version 11.0.0 (Red Hat 11.0.0-1.0.1.module+el8.4.0+20046+39fed697)
> 43 3.87 rockylinux:8 : Ok gcc (GCC) 8.4.1 20200928 (Red Hat 8.4.1-1) , clang version 11.0.0 (Red Hat 11.0.0-1.module+el8.4.0+412+05cf643f)
> 44 3.97 ubuntu:16.04 : Ok gcc (Ubuntu 5.4.0-6ubuntu1~16.04.12) 5.4.0 20160609 , clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
> 45 4.37 ubuntu:18.04 : Ok gcc (Ubuntu 7.5.0-3ubuntu1~18.04) 7.5.0 , clang version 6.0.0-1ubuntu2 (tags/RELEASE_600/final)
> 46 4.87 ubuntu:20.04 : Ok gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0 , clang version 10.0.0-4ubuntu1
> 47 4.47 ubuntu:20.10 : Ok gcc (Ubuntu 10.3.0-1ubuntu1~20.10) 10.3.0 , Ubuntu clang version 11.0.0-2
> 48 4.27 ubuntu:21.04 : Ok gcc (Ubuntu 10.3.0-1ubuntu1) 10.3.0 , Ubuntu clang version 12.0.0-3ubuntu1~21.04.1
> 49 4.37 ubuntu:21.10 : Ok gcc (Ubuntu 11.2.0-1ubuntu2) 11.2.0 , Ubuntu clang version 12.0.1-1
>
> $

--

- Arnaldo