Re: [PATCH 17/23] modpost: perform srcversion hashing in parallel

On Sat, Sep 12, 2026 at 01:50:00PM +0200, Yann Droneaud wrote:

Hi,

Le 08/09/2026 à 22:55, Lorenzo Stoakes (ARM) a écrit :

quoted

modpost does a lot of single-threaded work hashing files from each object's
.cmd file.

This makes the build slower than it needs to be, so do this work in
parallel.

If you're going parallel, it would be nicer to do it under make's jobserver
supervision.

Ack, though this patch is going to be dropped due to mod versions being removed
upstream.

quoted

This is egregious for allmodconfig builds - for instance x86-64 can end up
opening 200,000 files individually and hashing them all serially.

Parallelise this operation by maintaining a thread pool for the hashing
work.

Combined with the per-file hashing commit this cuts modpost's run time
nearly in half for an allmodconfig build.

Module.symvers and every *.mod.S are byte for byte the same.

modpost is on the serial tail of every allmodconfig build, however
defconfig does not set CONFIG_MODULE_SRCVERSION_ALL and is unchanged.

Whole build, 128-thread Threadripper 9980X, best of N runs:

                                          before   after     delta
                                          -------------------------------
   x86 allmodconfig, touch mm/vma.c, gcc    33.4s    30.2s     -3.2s (-10%)
   x86 allmodconfig, touch mm/vma.c, clang  31.1s    28.1s     -3.0s (-10%)

Assisted-by: LLM
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---
  scripts/mod/Makefile     |  1 +
  scripts/mod/modpost.c    | 72 ++++++++++++++++++++++++++++++++++++++++++++++--
  scripts/mod/modpost.h    |  2 ++
  scripts/mod/sumversion.c |  3 +-
  4 files changed, 74 insertions(+), 4 deletions(-)

Regards.

--
Cheers, Lorenzo