Re: [PATCH v2 1/2] tools/mm: add a standalone GUP microbenchmark

[Mike Rapoport]

(added broonie)

Hi,

On Tue, May 19, 2026 at 05:35:05PM +0530, 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 same matrix of
> configurations as run_gup_matrix() in run_vmtests.sh: all 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.
> 
> 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
> run_gup_matrix() in run_vmtests.sh. The standalone CLI and tools/mm
> integration are added here so tools/mm does not depend on kselftest.
> 
> Add gup_bench to BUILD_TARGETS and INSTALL_TARGETS in tools/mm/Makefile,
> 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@xxxxxxxxxx>
> Signed-off-by: Sarthak Sharma <sarthak.sharma@xxxxxxx>
> ---
>  MAINTAINERS          |   1 +
>  tools/mm/.gitignore  |   2 +
>  tools/mm/Makefile    |   6 +-
>  tools/mm/gup_bench.c | 491 +++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 497 insertions(+), 3 deletions(-)
>  create mode 100644 tools/mm/gup_bench.c

...
 
> +/*
> + * Local HugeTLB setup helpers for gup_bench.
> + *
> + * These helpers were copied from tools/testing/selftests/mm/ and adjusted to
> + * remove the ksft formatting. Keep this copy local so tools/mm does not
> + * depend on ksft output behavior.
> + */

It looks like self tests of at least 5 subsystems beside mm use hugetlb:

$ git grep -l "Hugepagesize:" tools/testing/selftests/ | grep -v "selftests/mm"
tools/testing/selftests/arm64/mte/check_hugetlb_options.c
tools/testing/selftests/cgroup/test_hugetlb_memcg.c
tools/testing/selftests/kvm/lib/test_util.c
tools/testing/selftests/memfd/common.c
tools/testing/selftests/net/tcp_mmap.c

It seems that we need to better share the common code in
tools/testing/selftest.

And adding another copy of the hugetlb detection and setup code does not
seem like a great idea.

> +
> +static unsigned int psize(void)
> +{
> +	static unsigned int __page_size;
> +
> +	if (!__page_size)
> +		__page_size = sysconf(_SC_PAGESIZE);
> +	return __page_size;
> +}
> +
> +static unsigned long default_huge_page_size(void)
> +{
> +	FILE *f = fopen("/proc/meminfo", "r");
> +	unsigned long hpage_size = 0;
> +	char buf[256];
> +
> +	if (!f)
> +		return 0;
> +	while (fgets(buf, sizeof(buf), f)) {
> +		if (sscanf(buf, "Hugepagesize:       %lu kB", &hpage_size) == 1)
> +			break;
> +	}
> +	fclose(f);
> +	hpage_size <<= 10;
> +	return hpage_size;
> +}

-- 
Sincerely yours,
Mike.