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Date: Wed, 10 Oct 2018 15:26:55 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Keith Busch <keith.busch@...el.com>
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
Dave Hansen <dave.hansen@...el.com>,
Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 1/6] mm/gup_benchmark: Time put_page
On Wed, 10 Oct 2018 13:56:00 -0600 Keith Busch <keith.busch@...el.com> 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?
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