Re: [PATCH 13/23] modpost: hash module source per-file, not per-byte

[Lorenzo Stoakes (ARM)]

On Fri, Sep 11, 2026 at 01:57:34PM +0200, Petr Pavlu wrote:
> On 9/11/26 12:41 PM, Lorenzo Stoakes (ARM) wrote:
> > On Thu, Sep 10, 2026 at 02:52:50PM +0200, Petr Pavlu wrote:
> >> On 9/8/26 10:55 PM, Lorenzo Stoakes (ARM) wrote:
> >>> modpost spends a long time md4 hashing module source at a per-byte
> >>> granularity.
> >>>
> >>> Fix this by doing this hashing per-file instead by accumulating a per-file
> >>> buffer in parse_file().
> >>>
> >>> All 11,189 .mod.c files and Module.symvers were confirmed to be identical
> >>> with this change applied.
> >>>
> >>> This is especially impactful for allmodconfig incremental builds (where
> >>> CONFIG_MODULE_SRCVERSION_ALL is set).
> >>>
> >>> Whole build, 128-thread Threadripper 9980X, best of N runs:
> >>>
> >>>                                          before   after     delta
> >>>                                          -------------------------------
> >>>   x86 allmodconfig, touch mm/vma.c, gcc    40.6s    38.2s     -2.4s (-6%)
> >>>   x86 allmodconfig, touch mm/vma.c, clang  36.2s    35.0s     -1.2s (-3%)
> >>>
> >>> Assisted-by: LLM
> >>> Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
> >>> ---
> >>>  scripts/mod/sumversion.c | 56 +++++++++++++++++++++++++++++++++++++-----------
> >>>  1 file changed, 44 insertions(+), 12 deletions(-)
> >>
> >> Support for the module srcversion is being removed in "module: remove
> >> MODULE_VERSION() and srcversion" [1] and scripts/mod/sumversion.c should
> >> be gone completely.
> >
> > Hmm, that series doesn't remove the script though, is that planned as a follow up?
>
> My reply to that series [1] notes that it should also remove
> scripts/mod/sumversion.c. It should be done in the next version.

Ack!

>
> >
> > I guess I can drop this patch from the series then :) Also patch 17 I think?
>
> I agree. The module srcversion is no longer needed since build IDs are
> nowadays the standard mechanism for providing effectively the same
> functionality. While I'm not sure when the mentioned removal will land,
> reviewing and polishing this patch and patch 17 would IMO be wasteful at
> this point.

Ack, will drop them for v2 then and add a note to the cover clearly stating the
dependency!

>
> [1] https://lore.kernel.org/linux-modules/4e321525-708c-4964-9937-d94ea27e8d85@xxxxxxxx/
>
> --
> Thanks,
> Petr

--
Cheers, Lorenzo