In message: [PATCH v5.15 0/1] aufs: remove overhead for typically disabled
Yocto use case
on 26/03/2022 Paul Gortmaker wrote:
> After having looked at the AUFS stuff some for the Yocto uprev, what I
> wanted to look at a bit more was the raw patches, like the aufs5-mmap.patch
> which touches existing core kernel files like mmap.c and fork.c etc.
>
> It is worth noting that the Yocto use case is quite different from the
> typical RYO user who goes out and sources AUFS for themselves. In the
> Yocto use case, we have probably 99% of our users who implicitly have
> AUFS code present but disabled via Kconfig. In the RYO case the code
> is rarely ever disabled since it was intentionally put there to be used.
>
> For those of us who used preempt-rt patches from over a decade ago, we
> can remember instances where the present-and-enabled case got all the
> testing and use, and the present-but-disabled case might not even build.
>
> That means we should be paying extra attention to ensure the present but
> disabled case isn't leaving us open to regressions, or any size or
> performance burdens vs. the unpatched case with no AUFS code present.
>
> To that end, I noticed overhead in AUFS that would remain even when
> disabled that could be relatively easily avoided and I fix that here.
>
> Boot testing included AUFS disabled, =y and =m (plus insmod) cases, on
> the yocto v5.15.30 baseline with the previous AUFS update applied.
>
> The two changes made here for the non-MMU case are untested but hopefully
> "obviously" correct as parallels to the tested MMU instances.
merged.
Bruce
>
> Paul.
> ---
>
> Paul Gortmaker (1):
> aufs: reduce overhead for "code present but disabled" use case.
>
> include/linux/mm.h | 15 +++
> include/linux/mm_types.h | 4
> mm/Makefile | 3 ++-
> mm/mmap.c| 12 +++-
> 4 files changed, 32 insertions(+), 2 deletions(-)
>
> --
> 2.17.1
>
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