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

[Dev Jain <dev.jain@arm.com>]

On 20/05/26 2:25 pm, Mike Rapoport wrote:
> (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@kernel.org>
>> Signed-off-by: Sarthak Sharma <sarthak.sharma@arm.com>
>> ---
>>  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.


Does it sound too insane to just do some sort of #include "../testing/selftests/mm/..."
to use the common helpers?

> 
>> +
>> +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;
>> +}
>