Re: [PATCH] mm/gup_benchmark: use pin_user_pages for FOLL_LONGTERM flag

John Hubbard <jhubbard@xxxxxxxxxx> · Sat, 15 Aug 2020 19:05:05 -0700

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@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jérôme Glisse <jglisse@xxxxxxxxxx>
Cc: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Shuah Khan <shuah@xxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Barry Song <song.bao.hua@xxxxxxxxxxxxx>
---
  mm/gup_benchmark.c                         | 23 +++++++++++-----------
  tools/testing/selftests/vm/gup_benchmark.c | 14 ++++++-------
  2 files changed, 19 insertions(+), 18 deletions(-)
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Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx>

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;








