linux-kernel - Re: [PATCHv4 3/3] mm/gup_benchemark: add LONGTERM

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Date:   Thu, 13 Jun 2019 14:42:47 -0700
From:   Ira Weiny <ira.weiny@...el.com>
To:     Pingfan Liu <kernelfans@...il.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Matthew Wilcox <willy@...radead.org>,
        John Hubbard <jhubbard@...dia.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Keith Busch <keith.busch@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 3/3] mm/gup_benchemark: add LONGTERM_BENCHMARK test in
 gup fast path

On Thu, Jun 13, 2019 at 06:45:02PM +0800, Pingfan Liu wrote:
> Introduce a GUP_LONGTERM_BENCHMARK ioctl to test longterm pin in gup fast
> path.
> 
> Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Mike Rapoport <rppt@...ux.ibm.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Matthew Wilcox <willy@...radead.org>
> Cc: John Hubbard <jhubbard@...dia.com>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>
> Cc: Keith Busch <keith.busch@...el.com>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Shuah Khan <shuah@...nel.org>
> Cc: linux-kernel@...r.kernel.org
> ---
>  mm/gup_benchmark.c                         | 11 +++++++++--
>  tools/testing/selftests/vm/gup_benchmark.c | 10 +++++++---
>  2 files changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/mm/gup_benchmark.c b/mm/gup_benchmark.c
> index 7dd602d..83f3378 100644
> --- a/mm/gup_benchmark.c
> +++ b/mm/gup_benchmark.c
> @@ -6,8 +6,9 @@
>  #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 GUP_FAST_LONGTERM_BENCHMARK	_IOWR('g', 2, struct gup_benchmark)
> +#define GUP_LONGTERM_BENCHMARK	_IOWR('g', 3, struct gup_benchmark)
> +#define GUP_BENCHMARK		_IOWR('g', 4, struct gup_benchmark)

But I really like this addition!  Thanks!

But why not just add GUP_FAST_LONGTERM_BENCHMARK to the end of this list (value
4)?  I know the user space test program is probably expected to be lock step
with this code but it seems odd to redefine GUP_LONGTERM_BENCHMARK and
GUP_BENCHMARK with this change.

Ira

>  
>  struct gup_benchmark {
>  	__u64 get_delta_usec;
> @@ -53,6 +54,11 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
>  			nr = get_user_pages_fast(addr, nr, gup->flags & 1,
>  						 pages + i);
>  			break;
> +		case GUP_FAST_LONGTERM_BENCHMARK:
> +			nr = get_user_pages_fast(addr, nr,
> +					(gup->flags & 1) | FOLL_LONGTERM,
> +					 pages + i);
> +			break;
>  		case GUP_LONGTERM_BENCHMARK:
>  			nr = get_user_pages(addr, nr,
>  					    (gup->flags & 1) | FOLL_LONGTERM,
> @@ -96,6 +102,7 @@ static long gup_benchmark_ioctl(struct file *filep, unsigned int cmd,
>  
>  	switch (cmd) {
>  	case GUP_FAST_BENCHMARK:
> +	case GUP_FAST_LONGTERM_BENCHMARK:
>  	case GUP_LONGTERM_BENCHMARK:
>  	case GUP_BENCHMARK:
>  		break;
> diff --git a/tools/testing/selftests/vm/gup_benchmark.c b/tools/testing/selftests/vm/gup_benchmark.c
> index c0534e2..ade8acb 100644
> --- a/tools/testing/selftests/vm/gup_benchmark.c
> +++ b/tools/testing/selftests/vm/gup_benchmark.c
> @@ -15,8 +15,9 @@
>  #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_FAST_LONGTERM_BENCHMARK	_IOWR('g', 2, struct gup_benchmark)
> +#define GUP_LONGTERM_BENCHMARK	_IOWR('g', 3, struct gup_benchmark)
> +#define GUP_BENCHMARK		_IOWR('g', 4, struct gup_benchmark)
>  
>  struct gup_benchmark {
>  	__u64 get_delta_usec;
> @@ -37,7 +38,7 @@ int main(int argc, char **argv)
>  	char *file = "/dev/zero";
>  	char *p;
>  
> -	while ((opt = getopt(argc, argv, "m:r:n:f:tTLUSH")) != -1) {
> +	while ((opt = getopt(argc, argv, "m:r:n:f:tTlLUSH")) != -1) {
>  		switch (opt) {
>  		case 'm':
>  			size = atoi(optarg) * MB;
> @@ -54,6 +55,9 @@ int main(int argc, char **argv)
>  		case 'T':
>  			thp = 0;
>  			break;
> +		case 'l':
> +			cmd = GUP_FAST_LONGTERM_BENCHMARK;
> +			break;
>  		case 'L':
>  			cmd = GUP_LONGTERM_BENCHMARK;
>  			break;
> -- 
> 2.7.5
>