Re: [PATCH v2 1/2] selftest/vm: Use correct PAGE_SHIFT value for ppc64

[Mike Rapoport <rppt@kernel.org>]

On Fri, Feb 11, 2022 at 12:03:28PM +0530, Aneesh Kumar K.V wrote:
> Keep it simple by using a #define and limiting hugepage size to 2M.
> This keeps the test simpler instead of dynamically finding the page size
> and huge page size.
> 
> Without this tests are broken w.r.t reading /proc/self/pagemap
> 
> 	if (pread(pagemap_fd, ent, sizeof(ent),
> 			(uintptr_t)ptr >> (PAGE_SHIFT - 3)) != sizeof(ent))
> 		err(2, "read pagemap");
> 
> Cc: Shuah Khan <shuah@kernel.org>
> Cc: linux-kselftest@vger.kernel.org
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
> ---
>  tools/testing/selftests/vm/ksm_tests.c        | 9 ++++++++-
>  tools/testing/selftests/vm/transhuge-stress.c | 9 ++++++++-
>  2 files changed, 16 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
> index 1436e1a9a3d3..cae72872152b 100644
> --- a/tools/testing/selftests/vm/ksm_tests.c
> +++ b/tools/testing/selftests/vm/ksm_tests.c
> @@ -22,7 +22,14 @@
>  #define KSM_MERGE_ACROSS_NODES_DEFAULT true
>  #define MB (1ul << 20)
>  
> -#define PAGE_SHIFT 12
> +#ifdef __powerpc64__
> +#define PAGE_SHIFT	16
> +#else
> +#define PAGE_SHIFT	12
> +#endif

Page size can be other than 4096 for other configurations as well. And even
on ppc64 it's not necessarily 64k.

Ideally page size in selftests/vm should be sysconf(_SC_PAGESIZE)

> +/*
> + * On ppc64 this will only work with radix 2M hugepage size
> + */
>  #define HPAGE_SHIFT 21
>  
>  #define PAGE_SIZE (1 << PAGE_SHIFT)
> diff --git a/tools/testing/selftests/vm/transhuge-stress.c b/tools/testing/selftests/vm/transhuge-stress.c
> index 5e4c036f6ad3..b1f8d98355c5 100644
> --- a/tools/testing/selftests/vm/transhuge-stress.c
> +++ b/tools/testing/selftests/vm/transhuge-stress.c
> @@ -16,7 +16,14 @@
>  #include <string.h>
>  #include <sys/mman.h>
>  
> -#define PAGE_SHIFT 12
> +#ifdef __powerpc64__
> +#define PAGE_SHIFT	16
> +#else
> +#define PAGE_SHIFT	12
> +#endif
> +/*
> + * On ppc64 this will only work with radix 2M hugepage size
> + */
>  #define HPAGE_SHIFT 21
>  
>  #define PAGE_SIZE (1 << PAGE_SHIFT)
> -- 
> 2.34.1
> 
> 

-- 
Sincerely yours,
Mike.