[PATCH 0/2] ring-buffer/selftest: Meta-page testing improvements

[PATCH 0/2] ring-buffer/selftest: Meta-page testing improvements

[Vincent Donnefort]

Following the comments on the original patch [1] here's a set of 2 patches to
improve the selftest.

[1] https://lore.kernel.org/all/20240628104611.1443542-1-vdonnefort@google.com/

Vincent Donnefort (2):
  ring-buffer/selftest: Verify the entire meta-page padding
  ring-buffer/selftest: Handle meta-page bigger than the system

 tools/testing/selftests/ring-buffer/map_test.c | 18 ++++++++++++++----
 1 file changed, 14 insertions(+), 4 deletions(-)


base-commit: 2fcd5aff92aab479a9a89cfce2dbc9c6a9455b4f
-- 
2.46.0.598.g6f2099f65c-goog

[PATCH 1/2] ring-buffer/selftest: Verify the entire meta-page padding

[Vincent Donnefort]

Improve the ring-buffer meta-page test coverage by checking for the
entire padding region to be 0 instead of just looking at the first 4
bytes.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index 4bb0192e43f3..ba12fd31de87 100644
--- a/tools/testing/selftests/ring-buffer/map_test.c
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -231,15 +231,15 @@ TEST_F(map, data_mmap)
 
 	/* Verify meta-page padding */
 	if (desc->meta->meta_page_size > getpagesize()) {
-		void *addr;
-
 		data_len = desc->meta->meta_page_size;
 		data = mmap(NULL, data_len,
 			    PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
 		ASSERT_NE(data, MAP_FAILED);
 
-		addr = (void *)((unsigned long)data + getpagesize());
-		ASSERT_EQ(*((int *)addr), 0);
+		for (int i = desc->meta->meta_struct_len;
+		     i < desc->meta->meta_page_size; i += sizeof(int))
+			ASSERT_EQ(*(int *)(data + i), 0);
+
 		munmap(data, data_len);
 	}
 }
-- 
2.46.0.598.g6f2099f65c-goog

[PATCH 2/2] ring-buffer/selftest: Handle meta-page bigger than the system

[Vincent Donnefort]

Handle the case where the meta-page content is bigger than the system
page-size. This prepares the ground for extending features covered by
the meta-page.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index ba12fd31de87..d10a847130fb 100644
--- a/tools/testing/selftests/ring-buffer/map_test.c
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -92,12 +92,22 @@ int tracefs_cpu_map(struct tracefs_cpu_map_desc *desc, int cpu)
 	if (desc->cpu_fd < 0)
 		return -ENODEV;
 
+again:
 	map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
 	if (map == MAP_FAILED)
 		return -errno;
 
 	desc->meta = (struct trace_buffer_meta *)map;
 
+	/* the meta-page is bigger than the original mapping */
+	if (page_size < desc->meta->meta_struct_len) {
+		int meta_page_size = desc->meta->meta_page_size;
+
+		munmap(desc->meta, page_size);
+		page_size = meta_page_size;
+		goto again;
+	}
+
 	return 0;
 }
 
-- 
2.46.0.598.g6f2099f65c-goog

Re: [PATCH 0/2] ring-buffer/selftest: Meta-page testing improvements

[Steven Rostedt]

On Tue, 10 Sep 2024 15:43:21 +0100
Vincent Donnefort <vdonnefort@google.com> wrote:

> Following the comments on the original patch [1] here's a set of 2 patches to
> improve the selftest.
> 
> [1] https://lore.kernel.org/all/20240628104611.1443542-1-vdonnefort@google.com/

This looks good, but can you resend this and Cc:

  Shuah Khan <skhan@linuxfoundation.org>
  linux-kselftest@vger.kernel.org

Thanks,

-- Steve

> 
> Vincent Donnefort (2):
>   ring-buffer/selftest: Verify the entire meta-page padding
>   ring-buffer/selftest: Handle meta-page bigger than the system
> 
>  tools/testing/selftests/ring-buffer/map_test.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
> 
> 
> base-commit: 2fcd5aff92aab479a9a89cfce2dbc9c6a9455b4f

Re: [PATCH v2] ring-buffer: Align meta-page to sub-buffers for improved TLB usage

[Steven Rostedt]

On Fri, 28 Jun 2024 11:46:11 +0100
Vincent Donnefort <vdonnefort@google.com> wrote:

> diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
> index a9006fa7097e..4bb0192e43f3 100644
> --- a/tools/testing/selftests/ring-buffer/map_test.c
> +++ b/tools/testing/selftests/ring-buffer/map_test.c
> @@ -228,6 +228,20 @@ TEST_F(map, data_mmap)
>  	data = mmap(NULL, data_len, PROT_READ, MAP_SHARED,
>  		    desc->cpu_fd, meta_len);
>  	ASSERT_EQ(data, MAP_FAILED);
> +
> +	/* Verify meta-page padding */
> +	if (desc->meta->meta_page_size > getpagesize()) {
> +		void *addr;
> +
> +		data_len = desc->meta->meta_page_size;
> +		data = mmap(NULL, data_len,
> +			    PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
> +		ASSERT_NE(data, MAP_FAILED);
> +
> +		addr = (void *)((unsigned long)data + getpagesize());
> +		ASSERT_EQ(*((int *)addr), 0);

Should we make this a test that the entire page is zero?

		for (int i = desc->meta->meta_struct_len; i < desc->meta->meta_page_size; i += sizeof(int))
			ASSERT_EQ(((int *)data)[i], 0);

?

> +		munmap(data, data_len);
> +	}
>  }

Also, looking at the init, if for some reason (I highly doubt it may
happen) that the meta_struct_len becomes bigger than page_size, we should
update the init section to:

	/* Handle the case where meta_struct_len is greater than page size */
	if (page_size < desc->meta->meta_struct_len) {
		/* meta_page_size is >= meta_struct_len */
		page_size = desc->meta->meta_page_size;
		munmap(desc->meta, page_size);
		map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
		if (map == MAP_FAILED)
			return -errno;
		desc->meta = (struct trace_buffer_meta *)map;
	}

-- Steve

[PATCH 1/2] ring-buffer/selftest: Verify the entire meta-page padding

[Vincent Donnefort]

Improve the ring-buffer meta-page test coverage by checking for the
entire padding region to be 0 instead of just looking at the first 4
bytes.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

--

Hi,

I saw you have sent "Align meta-page to sub-buffers for improved TLB usage" to
linux-next, so here's a follow-up patch addressing your comments, not sure if
you want to squash it or to put it on top.

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index 4bb0192e43f3..ba12fd31de87 100644
--- a/tools/testing/selftests/ring-buffer/map_test.c
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -231,15 +231,15 @@ TEST_F(map, data_mmap)
 
 	/* Verify meta-page padding */
 	if (desc->meta->meta_page_size > getpagesize()) {
-		void *addr;
-
 		data_len = desc->meta->meta_page_size;
 		data = mmap(NULL, data_len,
 			    PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
 		ASSERT_NE(data, MAP_FAILED);
 
-		addr = (void *)((unsigned long)data + getpagesize());
-		ASSERT_EQ(*((int *)addr), 0);
+		for (int i = desc->meta->meta_struct_len;
+		     i < desc->meta->meta_page_size; i += sizeof(int))
+			ASSERT_EQ(*(int *)(data + i), 0);
+
 		munmap(data, data_len);
 	}
 }

base-commit: 2a07e30c19f391af26517c409fd66e401c6f4ee7
prerequisite-patch-id: 16b79d676c5faf3b57443b576976c7522fcd5a4b
-- 
2.46.0.295.g3b9ea8a38a-goog

[PATCH 2/2] ring-buffer/selftest: Handle meta-page bigger than the system

[Vincent Donnefort]

Handle the case where the meta-page content is bigger than the system
page-size. This prepares the ground for extending features covered by
the meta-page.

Signed-off-by: Vincent Donnefort <vdonnefort@google.com>

diff --git a/tools/testing/selftests/ring-buffer/map_test.c b/tools/testing/selftests/ring-buffer/map_test.c
index ba12fd31de87..d10a847130fb 100644
--- a/tools/testing/selftests/ring-buffer/map_test.c
+++ b/tools/testing/selftests/ring-buffer/map_test.c
@@ -92,12 +92,22 @@ int tracefs_cpu_map(struct tracefs_cpu_map_desc *desc, int cpu)
 	if (desc->cpu_fd < 0)
 		return -ENODEV;
 
+again:
 	map = mmap(NULL, page_size, PROT_READ, MAP_SHARED, desc->cpu_fd, 0);
 	if (map == MAP_FAILED)
 		return -errno;
 
 	desc->meta = (struct trace_buffer_meta *)map;
 
+	/* the meta-page is bigger than the original mapping */
+	if (page_size < desc->meta->meta_struct_len) {
+		int meta_page_size = desc->meta->meta_page_size;
+
+		munmap(desc->meta, page_size);
+		page_size = meta_page_size;
+		goto again;
+	}
+
 	return 0;
 }
 
-- 
2.46.0.295.g3b9ea8a38a-goog