On Wed, 10 Oct 2018 13:56:00 -0600 Keith Busch <keith.busch@xxxxxxxxx> wrote:
> We'd like to measure time to unpin user pages, so this adds a second
> benchmark timer on put_page, separate from get_page.
>
> Adding the field will breaks this ioctl ABI, but should be okay since
> this an in-tree kernel selftest.
>
> ...
>
> --- a/mm/gup_benchmark.c
> +++ b/mm/gup_benchmark.c
> @@ -8,7 +8,8 @@
> #define GUP_FAST_BENCHMARK _IOWR('g', 1, struct gup_benchmark)
>
> struct gup_benchmark {
> - __u64 delta_usec;
> + __u64 get_delta_usec;
> + __u64 put_delta_usec;
> __u64 addr;
> __u64 size;
> __u32 nr_pages_per_call;
If we move put_delta_usec to the end of this struct, the ABI remains
back-compatible?
