Re: [PATCH v5 4/5] tools/mm: add a standalone GUP microbenchmark

["David Hildenbrand (Arm)" <david@kernel.org>]

On 7/16/26 14:32, Sarthak Sharma wrote:
> Add a command-line tool for benchmarking get_user_pages fast-path
> (GUP_FAST), pin_user_pages fast-path (PIN_FAST), and pin_user_pages
> longterm (PIN_LONGTERM) via the CONFIG_GUP_TEST debugfs interface.
> 
> When invoked without arguments, gup_bench runs the benchmark subset
> of configurations covered by run_gup_matrix() in run_vmtests.sh: all

To we really need the matrix in there? The matrix was good for selftests, but
not when using it as a benchmarking tool, no?

> three GUP commands across read/write, private/shared mappings, and a
> range of page counts, with THP on/off for regular mappings and hugetlb
> for huge page mappings. Restore HugeTLB settings after each hugetlb
> benchmark run. Validate numeric command-line arguments instead of
> relying on atoi().
> 
> This tool is a mix of reused and new logic. The mapping/setup path comes
> from selftests/mm/gup_test.c, while the default benchmark matrix matches
> the benchmark subset of run_gup_matrix() in run_vmtests.sh. The standalone
> CLI and tools/mm integration are added here and the HugeTLB setup code is
> shared via tools/lib/mm.
> 
> Add gup_bench to BUILD_TARGETS and INSTALL_TARGETS in tools/mm/Makefile,
> link it against the shared tools/lib/mm hugepage helpers, and ignore the
> resulting binary in tools/mm/.gitignore. While here, also add the
> missing thp_swap_allocator_test entry to .gitignore.
> 
> Add tools/mm/gup_bench.c to the GUP entry in MAINTAINERS.
> 
> Suggested-by: David Hildenbrand (Arm) <david@kernel.org>
> Signed-off-by: Sarthak Sharma <sarthak.sharma@arm.com>
> ---
>  MAINTAINERS          |   1 +
>  tools/mm/.gitignore  |   2 +
>  tools/mm/Makefile    |  10 +-
>  tools/mm/gup_bench.c | 482 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 492 insertions(+), 3 deletions(-)
>  create mode 100644 tools/mm/gup_bench.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 26b06d80ab45..7d121dee9f0f 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -17024,6 +17024,7 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
>  F:	mm/gup.c
>  F:	mm/gup_test.c
>  F:	mm/gup_test.h
> +F:	tools/mm/gup_bench.c
>  F:	tools/testing/selftests/mm/gup_longterm.c
>  F:	tools/testing/selftests/mm/gup_test.c
>  
> diff --git a/tools/mm/.gitignore b/tools/mm/.gitignore
> index 922879f93fc8..154d740be02e 100644
> --- a/tools/mm/.gitignore
> +++ b/tools/mm/.gitignore
> @@ -2,3 +2,5 @@
>  slabinfo
>  page-types
>  page_owner_sort
> +thp_swap_allocator_test

^ Does that belong into this patch?

> +gup_bench

I wonder if it makes sense to "git mv" the existing tool (only slightly fixing
header inclusion to make it compile), essentially removing the old benchmark.

So it would be

1) Move tools, fixing up includes and removing the gup testing logic+matrix to
   make it compile

2) Extend tool by XYZ

3) Add completely new selftest

Because looking at patch #5, there is not really any code reuse there, but I
suspect there should be some in this patch here when moving instead of copying.

That would make this a lot easier to review.

-- 
Cheers,

David