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Date: Sat, 15 Aug 2020 19:05:05 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Barry Song <song.bao.hua@...ilicon.com>,
<akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
<linux-kselftest@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC: <linuxarm@...wei.com>, Jan Kara <jack@...e.cz>,
Jérôme Glisse <jglisse@...hat.com>,
"Matthew Wilcox (Oracle)" <willy@...radead.org>,
Al Viro <viro@...iv.linux.org.uk>,
"Christoph Hellwig" <hch@...radead.org>,
Dan Williams <dan.j.williams@...el.com>,
"Dave Chinner" <david@...morbit.com>,
Jason Gunthorpe <jgg@...pe.ca>,
"Jonathan Corbet" <corbet@....net>, Michal Hocko <mhocko@...e.com>,
Mike Kravetz <mike.kravetz@...cle.com>,
Shuah Khan <shuah@...nel.org>, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH] mm/gup_benchmark: use pin_user_pages for FOLL_LONGTERM
flag
On 8/15/20 5:20 AM, Barry Song wrote:
> According to Documentation/core-api/pin_user_pages.rst, FOLL_PIN is a
> prerequisite to FOLL_LONGTERM. Another way of saying that is,
> FOLL_LONGTERM is a specific case, more restrictive case of FOLL_PIN.
>
> Almost all kernel modules are using pin_user_pages() with FOLL_LONGTERM,
> mm/gup_benchmark.c seems to the only exception in which FOLL_PIN is not
> a prerequisite to FOLL_LONGTERM.
>
> Cc: John Hubbard <jhubbard@...dia.com>
> Cc: Jan Kara <jack@...e.cz>
> Cc: Jérôme Glisse <jglisse@...hat.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@...radead.org>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Dave Chinner <david@...morbit.com>
> Cc: Jason Gunthorpe <jgg@...pe.ca>
> Cc: Jonathan Corbet <corbet@....net>
> Cc: Michal Hocko <mhocko@...e.com>
> Cc: Mike Kravetz <mike.kravetz@...cle.com>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Signed-off-by: Barry Song <song.bao.hua@...ilicon.com>
> ---
> mm/gup_benchmark.c | 23 +++++++++++-----------
> tools/testing/selftests/vm/gup_benchmark.c | 14 ++++++-------
> 2 files changed, 19 insertions(+), 18 deletions(-)
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vqEWLfitNguIA
Reviewed-by: John Hubbard <jhubbard@...dia.com>
thanks,
--
John Hubbard
NVIDIA
>
> diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
> index be690fa66a46..464cae1fa3ea 100644
> --- a/mm/gup_benchmark.c
> +++ b/mm/gup_benchmark.c
> @@ -6,10 +6,10 @@
> #include <linux/debugfs.h>
>
> #define GUP_FAST_BENCHMARK _IOWR('g', 1, struct gup_benchmark)
> -#define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
> -#define GUP_BENCHMARK _IOWR('g', 3, struct gup_benchmark)
> -#define PIN_FAST_BENCHMARK _IOWR('g', 4, struct gup_benchmark)
> -#define PIN_BENCHMARK _IOWR('g', 5, struct gup_benchmark)
> +#define GUP_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
> +#define PIN_FAST_BENCHMARK _IOWR('g', 3, struct gup_benchmark)
> +#define PIN_BENCHMARK _IOWR('g', 4, struct gup_benchmark)
> +#define PIN_LONGTERM_BENCHMARK _IOWR('g', 5, struct gup_benchmark)
>
> struct gup_benchmark {
> __u64 get_delta_usec;
> @@ -28,7 +28,6 @@ static void put_back_pages(unsigned int cmd, struct page **pages,
>
> switch (cmd) {
> case GUP_FAST_BENCHMARK:
> - case GUP_LONGTERM_BENCHMARK:
> case GUP_BENCHMARK:
> for (i = 0; i < nr_pages; i++)
> put_page(pages[i]);
> @@ -36,6 +35,7 @@ static void put_back_pages(unsigned int cmd, struct page **pages,
>
> case PIN_FAST_BENCHMARK:
> case PIN_BENCHMARK:
> + case PIN_LONGTERM_BENCHMARK:
> unpin_user_pages(pages, nr_pages);
> break;
> }
> @@ -50,6 +50,7 @@ static void verify_dma_pinned(unsigned int cmd, struct page **pages,
> switch (cmd) {
> case PIN_FAST_BENCHMARK:
> case PIN_BENCHMARK:
> + case PIN_LONGTERM_BENCHMARK:
> for (i = 0; i < nr_pages; i++) {
> page = pages[i];
> if (WARN(!page_maybe_dma_pinned(page),
> @@ -101,11 +102,6 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
> nr = get_user_pages_fast(addr, nr, gup->flags,
> pages + i);
> break;
> - case GUP_LONGTERM_BENCHMARK:
> - nr = get_user_pages(addr, nr,
> - gup->flags | FOLL_LONGTERM,
> - pages + i, NULL);
> - break;
> case GUP_BENCHMARK:
> nr = get_user_pages(addr, nr, gup->flags, pages + i,
> NULL);
> @@ -118,6 +114,11 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
> nr = pin_user_pages(addr, nr, gup->flags, pages + i,
> NULL);
> break;
> + case PIN_LONGTERM_BENCHMARK:
> + nr = pin_user_pages(addr, nr,
> + gup->flags | FOLL_LONGTERM,
> + pages + i, NULL);
> + break;
> default:
> kvfree(pages);
> ret = -EINVAL;
> @@ -162,10 +163,10 @@ static long gup_benchmark_ioctl(struct file *filep, unsigned int cmd,
>
> switch (cmd) {
> case GUP_FAST_BENCHMARK:
> - case GUP_LONGTERM_BENCHMARK:
> case GUP_BENCHMARK:
> case PIN_FAST_BENCHMARK:
> case PIN_BENCHMARK:
> + case PIN_LONGTERM_BENCHMARK:
> break;
> default:
> return -EINVAL;
> diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c
> index 43b4dfe161a2..31f8bb086907 100644
> --- a/tools/testing/selftests/vm/gup_benchmark.c
> +++ b/tools/testing/selftests/vm/gup_benchmark.c
> @@ -15,12 +15,12 @@
> #define PAGE_SIZE sysconf(_SC_PAGESIZE)
>
> #define GUP_FAST_BENCHMARK _IOWR('g', 1, struct gup_benchmark)
> -#define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
> -#define GUP_BENCHMARK _IOWR('g', 3, struct gup_benchmark)
> +#define GUP_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
>
> /* Similar to above, but use FOLL_PIN instead of FOLL_GET. */
> -#define PIN_FAST_BENCHMARK _IOWR('g', 4, struct gup_benchmark)
> -#define PIN_BENCHMARK _IOWR('g', 5, struct gup_benchmark)
> +#define PIN_FAST_BENCHMARK _IOWR('g', 3, struct gup_benchmark)
> +#define PIN_BENCHMARK _IOWR('g', 4, struct gup_benchmark)
> +#define PIN_LONGTERM_BENCHMARK _IOWR('g', 5, struct gup_benchmark)
>
> /* Just the flags we need, copied from mm.h: */
> #define FOLL_WRITE 0x01 /* check pte is writable */
> @@ -52,6 +52,9 @@ int main(int argc, char **argv)
> case 'b':
> cmd = PIN_BENCHMARK;
> break;
> + case 'L':
> + cmd = PIN_LONGTERM_BENCHMARK;
> + break;
> case 'm':
> size = atoi(optarg) * MB;
> break;
> @@ -67,9 +70,6 @@ int main(int argc, char **argv)
> case 'T':
> thp = 0;
> break;
> - case 'L':
> - cmd = GUP_LONGTERM_BENCHMARK;
> - break;
> case 'U':
> cmd = GUP_BENCHMARK;
> break;
>
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