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[PATCH 00/10] Tuning packages for CPU micro-architectures |
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Sat, 4 Dec 2021 21:34:47 +0100 |
Hello Guix!
This patch series is an attempt to allow users to build or
substitute packages for the very CPU they are using, as opposed
to using a generic binary that targets the baseline
architecture—e.g., x86_64 without AVX extensions.
As a reminder, my take on this is that The Right Thing is for
code to select optimized implementations for the host CPU at
load time, using (possibly hand-crafted) “function multi-versioning”:
https://hpc.guix.info/blog/2018/01/pre-built-binaries-vs-performance/
Now, there’s at least one situation where developers don’t do
“the right thing”: C++ header-only libraries. It turns out
header-only libraries with #ifdef’d SIMD code are quite common:
Eigen, xsimd, xtensor, etc. Every user of those libs has to be
compiled with ‘-march=native’ to take advantage of those
SIMD-optimized routines and there’s little hope of seeing those
libraries implement load-time or run-time selection¹.
This patch set implements “package multi-versioning”, where a package
can have different variants users may choose from: baseline, haswell,
skylake, etc. This is implemented as a package transformation option,
‘--tune’. Without any argument, ‘--tune’ grafts tuned package variants
for each package that has the ‘tunable?’ property. For example:
guix shell eigen-benchmarks --tune -- benchBlasGemm 16 16 16 100 100
runs one of the Eigen benchmarks tuned for the host CPU, because
‘eigen-benchmarks’ is marked as “tunable”.
This is achieved not by passing ‘-march=native’, because the daemon
might be running on a separate machine with a different CPU, but by
identifying the ‘-march’ value corresponding to the host CPU and
passing ‘-march’ to the compiler, via a wrapper.
On my skylake laptop, that gives a noticeable difference on the GEMM
benchmark of Eigen and good results on the xtensor benchmarks too,
unsurprisingly. I don’t have figures for higher-level applications,
but it’d be nice to benchmark some of Eigen’s dependents for instance,
as shown by:
guix graph -M2 -t reverse-package eigen | xdot -f fdp -
If you could run such benchmarks, that’d be great! :-)
Things like Fenics may benefit from it.
Nix people chose to introduce separate system types for the various
x86_64 micro-architecture levels: x86_64-linux-v1, x86_64-linux-v2,
etc.² I think this is somewhat wasteful and unpractical though.
It’s also unclear whether those levels, defined in the new x86_64
psABI³, are a viable abstraction: vendors seem to be mixing features
rather than really following the accumulative pattern that those
levels imply.
Thoughts?
Ludo’.
¹
https://listengine.tuxfamily.org/lists.tuxfamily.org/eigen/2021/11/msg00006.html
² https://discourse.nixos.org/t/nix-2-4-released/15822
³
https://gitlab.com/x86-psABIs/x86-64-ABI/-/blob/master/x86-64-ABI/low-level-sys-info.tex
Ludovic Courtès (10):
Add (guix cpu).
transformations: Add '--tune'.
ci: Add extra jobs for tunable packages.
gnu: Add eigen-benchmarks.
gnu: Add xsimd-benchmark.
gnu: Add xtensor-benchmark.
gnu: ceres-solver: Mark as tunable.
gnu: Add ceres-solver-benchmarks.
gnu: libfive: Mark as tunable.
gnu: prusa-slicer: Mark as tunable.
Makefile.am | 1 +
doc/guix.texi | 54 ++++++++++++++
gnu/ci.scm | 43 ++++++++---
gnu/packages/algebra.scm | 79 ++++++++++++++++++++
gnu/packages/cpp.scm | 23 ++++++
gnu/packages/engineering.scm | 10 ++-
gnu/packages/maths.scm | 49 ++++++++++++-
guix/cpu.scm | 137 +++++++++++++++++++++++++++++++++++
guix/transformations.scm | 134 ++++++++++++++++++++++++++++++++++
tests/transformations.scm | 20 +++++
10 files changed, 538 insertions(+), 12 deletions(-)
create mode 100644 guix/cpu.scm
base-commit: 052f56e5a614854636563278ee5a2248b3609d87
prerequisite-patch-id: 7e5c2bb5942496daf01a7f6dfc1b0b5b214f1584
--
2.33.0
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--- Begin Message ---
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Subject: |
Re: bug#52283: [PATCH 00/10] Tuning packages for CPU micro-architectures |
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Date: |
Sat, 01 Jan 2022 15:59:00 +0100 |
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User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) |
Hello!
Ludovic Courtès <ludo@gnu.org> skribis:
> Here is v2 of the patch set implementing the ‘--tune’ package
> transformation option. Changes since v1:
Pushed!
40662f7da8 news: Add entry about '--tune'.
4cd0b37f6b gnu: gsl: Add 'tunable?' property.
1fcb98ca54 gnu: prusa-slicer: Mark as tunable.
6554294754 gnu: libfive: Mark as tunable.
6b70412370 gnu: Add ceres-solver-benchmarks.
24667081ad gnu: ceres-solver: Mark as tunable.
182b97dac0 gnu: Add xtensor-benchmark.
f5873949f3 gnu: Add xsimd-benchmark.
6542e5713a gnu: Add eigen-benchmarks.
6756c64a8f ci: Add extra jobs for tunable packages.
d090e9c37d transformations: Add '--tune'.
0a767f02d4 gnu: clang: Add 'compiler-cpu-architectures' property.
2576e2019d gnu: gcc: Add 'compiler-cpu-architectures' property.
a644f88d28 Add (guix cpu).
Ludo’.
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