[LTP] [PATCH] thp02: simplify test to lower memory requirements

[Li Wang]

On Fri, Oct 18, 2019 at 11:30 PM Jan Stancek <jstancek@redhat.com> wrote:

> Test is using 4 hugepages per allocation, and makes 4*3 allocations
> in total. This is problem for aarch64, where default huge page size
> is 512M. Systems are running into unexpected OOMs, because there
> is no check for available memory.
>
> Simplify test by:
> - dropping 3rd allocation, it's used only for pattern comparison
> - run test function in new child process, so we don't need to worry
>   about cleaning up after mremap() and it lowers overall memory
>   requirements
> - add a simple check if there's enough memory to setup()
> - drop .needs_root, there's no need for it
>
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> ---
>  testcases/kernel/mem/thp/thp02.c | 79
> +++++++++++++++++++++++++---------------
>  1 file changed, 50 insertions(+), 29 deletions(-)
>
> diff --git a/testcases/kernel/mem/thp/thp02.c
> b/testcases/kernel/mem/thp/thp02.c
> index 6502210e50de..4d0c929f91ff 100644
> --- a/testcases/kernel/mem/thp/thp02.c
> +++ b/testcases/kernel/mem/thp/thp02.c
> @@ -47,46 +47,62 @@
>  #ifdef HAVE_MREMAP_FIXED
>  static int ps;
>  static long hps, size;
> -static void *p, *p2, *p3, *p4;
> +
> +/*
> + * Will try to do the following 4 mremaps cases:
> + *   mremap(p, size-ps, size-ps, flag, p3);
> + *   mremap(p, size-ps, size-ps, flag, p3+ps);
> + *   mremap(p+ps, size-ps, size-ps, flag, p3);
> + *   mremap(p+ps, size-ps, size-ps, flag, p3+ps);
> + */
>

The comment should be updated too, otherwise patch LGTM.


> +static void do_child(int i)
> +{
> +       long j, remap_size;
> +       unsigned char *p1, *p2, *ret, *old_addr, *new_addr;
> +
> +       p1 = SAFE_MEMALIGN(hps, size);
> +       p2 = SAFE_MEMALIGN(hps, size);
> +
> +       memset(p1, 0xff, size);
> +       memset(p2, 0x77, size);
> +
> +       old_addr = p1 + ps * (i >> 1);
> +       new_addr = p2 + ps * (i & 1);
> +       remap_size = size - ps;
> +
> +       tst_res(TINFO, "mremap (%p-%p) to (%p-%p)",
> +               old_addr, old_addr + remap_size,
> +               new_addr, new_addr + remap_size);
> +
> +       ret = mremap(old_addr, remap_size, remap_size,
> +                   MREMAP_FIXED | MREMAP_MAYMOVE, new_addr);
> +       if (ret == MAP_FAILED)
> +               tst_brk(TBROK | TERRNO, "mremap");
> +
> +       for (j = 0; j < size - ps; j++) {
> +               if (ret[j] != 0xff)
> +                       tst_brk(TBROK, "mremap bug");
> +       }
> +
> +       exit(0);
> +}
>
>  static void do_mremap(void)
>  {
>         int i;
> -       void *old_addr, *new_addr;
>
>         for (i = 0; i < 4; i++) {
> -               p = SAFE_MEMALIGN(hps, size);
> -               p2 = SAFE_MEMALIGN(hps, size);
> -               p3 = SAFE_MEMALIGN(hps, size);
> -
> -               memset(p, 0xff, size);
> -               memset(p2, 0xff, size);
> -               memset(p3, 0x77, size);
> -
> -               /*
> -                * Will try to do the following 4 mremaps cases:
> -                *   mremap(p, size-ps, size-ps, flag, p3);
> -                *   mremap(p, size-ps, size-ps, flag, p3+ps);
> -                *   mremap(p+ps, size-ps, size-ps, flag, p3);
> -                *   mremap(p+ps, size-ps, size-ps, flag, p3+ps);
> -                */
> -               old_addr = p + ps * (i >> 1);
> -               new_addr = p3 + ps * (i & 1);
> -               tst_res(TINFO, "mremap %p to %p", old_addr, new_addr);
> -
> -               p4 = mremap(old_addr, size - ps, size - ps,
> -                           MREMAP_FIXED | MREMAP_MAYMOVE, new_addr);
> -               if (p4 == MAP_FAILED)
> -                       tst_brk(TBROK | TERRNO, "mremap");
> -               if (memcmp(p4, p2, size - ps))
> -                       tst_brk(TBROK, "mremap bug");
> +               if (SAFE_FORK() == 0)
> +                       do_child(i);
> +               tst_reap_children();
>         }
> -
>         tst_res(TPASS, "Still alive.");
>  }
>
>  static void setup(void)
>  {
> +       long memfree;
> +
>         if (access(PATH_THP, F_OK) == -1)
>                 tst_brk(TCONF, "THP not enabled in kernel?");
>
> @@ -95,12 +111,17 @@ static void setup(void)
>         ps = sysconf(_SC_PAGESIZE);
>         hps = SAFE_READ_MEMINFO("Hugepagesize:") * 1024;
>         size = hps * 4;
> +
> +       memfree = (SAFE_READ_MEMINFO("MemFree:") * 1024 +
> +               SAFE_READ_MEMINFO("Cached:") * 1024);
> +       if (memfree < size * 2)
> +               tst_brk(TCONF, "not enough memory");
>  }
>
>  static struct tst_test test = {
> -       .needs_root = 1,
>         .setup = setup,
>         .test_all = do_mremap,
> +       .forks_child = 1,
>  };
>
>  #else
> --
> 1.8.3.1
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>


-- 
Regards,
Li Wang
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