Re: [V2 PATCH 5/6] KVM: selftests: Add get_free_huge_2m_pages

Sean Christopherson
2023-01-17T22:37:35Z

On Mon, Dec 05, 2022, Vishal Annapurve wrote:
> Add an API to query free 2MB hugepages in the system.
>
> Signed-off-by: Vishal Annapurve <vannapurve@google.com>
> ---
> .../testing/selftests/kvm/include/test_util.h | 1 +
> tools/testing/selftests/kvm/lib/test_util.c | 18 ++++++++++++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
> index aea80071f2b8..3d1cc215940a 100644
> --- a/tools/testing/selftests/kvm/include/test_util.h
> +++ b/tools/testing/selftests/kvm/include/test_util.h
> @@ -122,6 +122,7 @@ struct vm_mem_backing_src_alias {
> bool thp_configured(void);
> size_t get_trans_hugepagesz(void);
> size_t get_def_hugetlb_pagesz(void);
> +size_t get_free_huge_2mb_pages(void);
> const struct vm_mem_backing_src_alias *vm_mem_backing_src_alias(uint32_t i);
> size_t get_backing_src_pagesz(uint32_t i);
> bool is_backing_src_hugetlb(uint32_t i);
> diff --git a/tools/testing/selftests/kvm/lib/test_util.c b/tools/testing/selftests/kvm/lib/test_util.c
> index d33b98bfe8a3..745573023b57 100644
> --- a/tools/testing/selftests/kvm/lib/test_util.c
> +++ b/tools/testing/selftests/kvm/lib/test_util.c
> @@ -162,6 +162,24 @@ size_t get_trans_hugepagesz(void)
> return size;
> }
>
> +size_t get_free_huge_2mb_pages(void)

I strongly prefer to follow the precedence set by other tests, which at this
point means defaulting to non-huge pages. I do think we need to make it easier
and/or automatic to test hugepages, but I would like to tackle that problem
separately. E.g. a kernel built without hugepage support will fail the fopen()
below.

> +{
> + size_t free_pages;
> + FILE *f;
> + int ret;
> +
> + f = fopen("/sys/kernel/mm/hugepages/hugepages-2048kB/free_hugepages", "r");
> + TEST_ASSERT(f != NULL, "Error in opening hugepages-2048kB/free_hugepages");
> +
> + do {
> + ret = fscanf(f, "%ld", &free_pages);
> + } while (errno == EINTR);
> + TEST_ASSERT(ret < 1, "Error reading hugepages-2048kB/free_hugepages");
> + fclose(f);
> +
> + return free_pages;
> +}
> +
> size_t get_def_hugetlb_pagesz(void)
> {
> char buf[64];
> --
> 2.39.0.rc0.267.gcb52ba06e7-goog
>