[LTP] [PATCH v1 1/1] migrate_pages03: remove wait_ksmd_full_scan() check because it's not necessary

[Li Wang]

Pengfei Xu <pengfei.xu@intel.com> wrote:

Remove wait_ksmd_full_scan() check because it's not a necessary step for
> migrate_pages03 syscall test:
> 1. KSM(kernel samepage merging) could be enabled and it is optional for
> migrate_pages syscall testing.
>

The wait_ksmd_full_scan guarantees the actual merging happens then test
can migrate those merged KSM pages to reproduce the regression panic in
kernel commit 4b0ece6fa0167b.

So this is a necessary configuration before testing.


> 2. When server launched any qemu guest, wait_ksmd_full_scan() will in
> infinite loop due to /sys/kernel/mm/ksm/full_scans number would not
> increase anymore, and migrate_pages03 will failed with timeout reason.
> After removed wait_ksmd_full_scan(), migrate_pages03 could pass without
> issue.


Yes, this timeout problem likely exists. That is the KSM design which can't
avoid "unrelated" page merging happening in the background.
But removing the wait_ksmd_full_scan might not be a good approach IMHO.

Cc @Andrea Arcangeli <aarcange@redhat.com> if he has good suggestions on
the test.


> Signed-off-by: Pengfei Xu <pengfei.xu@intel.com>
> ---
>  testcases/kernel/syscalls/migrate_pages/migrate_pages03.c | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/testcases/kernel/syscalls/migrate_pages/migrate_pages03.c
> b/testcases/kernel/syscalls/migrate_pages/migrate_pages03.c
> index 4d3299b61..f514ed10c 100644
> --- a/testcases/kernel/syscalls/migrate_pages/migrate_pages03.c
> +++ b/testcases/kernel/syscalls/migrate_pages/migrate_pages03.c
> @@ -95,7 +95,6 @@ static void setup(void)
>
>         SAFE_FILE_SCANF(PATH_KSM "run", "%d", &orig_ksm_run);
>         SAFE_FILE_PRINTF(PATH_KSM "run", "%d", 1);
> -       wait_ksmd_full_scan();
>  }
>
>  static void cleanup(void)
> --
> 2.43.0
>
>
> --
> Mailing list info: https://lists.linux.it/listinfo/ltp
>
>

-- 
Regards,
Li Wang