[LTP] [PATCH] io: fix really slow dio_sparse on certain systems

[LTP] [PATCH] io: fix really slow dio_sparse on certain systems

[Andrea Cervesato]

From: Andrea Cervesato <andrea.cervesato@suse.com>

The reason why dio_sparse is happening to be slow on certain systems is
that, if data buffering is slow, we run more buffered read() for one
single dio write(). This slows down the whole test, because for each
read() we always need to move data from kernel space to user space.

Create a READ_BUFFER_SIZE variable inside the common.h header and use
it to define the write buffer size.

Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
---
 testcases/kernel/io/ltp-aiodio/common.h     | 6 ++++--
 testcases/kernel/io/ltp-aiodio/dio_sparse.c | 2 +-
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/testcases/kernel/io/ltp-aiodio/common.h b/testcases/kernel/io/ltp-aiodio/common.h
index 9a2d2716661651adf40c635ac516cc70068c9393..d3f05a3c1e75cd4baa629cbce1872729a0d641c6 100644
--- a/testcases/kernel/io/ltp-aiodio/common.h
+++ b/testcases/kernel/io/ltp-aiodio/common.h
@@ -9,6 +9,8 @@
 #include <stdlib.h>
 #include "tst_test.h"
 
+#define READ_BUFFER_SIZE 4096
+
 static inline char *check_zero(char *buf, int size)
 {
 	char *p;
@@ -57,7 +59,7 @@ static inline void io_append(const char *path, char pattern, int flags, size_t b
 
 static inline void io_read(const char *filename, int filesize, volatile int *run_child)
 {
-	char buff[4096];
+	char buff[READ_BUFFER_SIZE];
 	int fd;
 	int i;
 	int r;
@@ -102,7 +104,7 @@ exit:
 
 static inline void io_read_eof(const char *filename, volatile int *run_child)
 {
-	char buff[4096];
+	char buff[READ_BUFFER_SIZE];
 	int fd;
 	int r;
 
diff --git a/testcases/kernel/io/ltp-aiodio/dio_sparse.c b/testcases/kernel/io/ltp-aiodio/dio_sparse.c
index c87e5ab1aca7c8910f76ee87f86b561f548d4cdf..d858340bf9a707fb019e82c644da7f355ad0effd 100644
--- a/testcases/kernel/io/ltp-aiodio/dio_sparse.c
+++ b/testcases/kernel/io/ltp-aiodio/dio_sparse.c
@@ -32,7 +32,7 @@ static char *str_filesize;
 static char *str_offset;
 
 static int numchildren = 16;
-static long long writesize = 1024;
+static long long writesize = READ_BUFFER_SIZE;
 static long long filesize = 100 * 1024 * 1024;
 static long long offset = 0;
 static long long alignment;

---
base-commit: c47ab95d5fe077133e598ac7762387450a87cb2b
change-id: 20260123-fix_dio_sparse_slow-925958767d74

Best regards,
-- 
Andrea Cervesato <andrea.cervesato@suse.com>


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Re: [LTP] [PATCH] io: fix really slow dio_sparse on certain systems

[Petr Vorel]

Hi Andrea,

> The reason why dio_sparse is happening to be slow on certain systems is
> that, if data buffering is slow, we run more buffered read() for one
> single dio write(). This slows down the whole test, because for each
> read() we always need to move data from kernel space to user space.

> Create a READ_BUFFER_SIZE variable inside the common.h header and use
> it to define the write buffer size.

LGTM. IMHO good for a release.

Kind regards,
Petr

> Signed-off-by: Andrea Cervesato <andrea.cervesato@suse.com>
> ---
>  testcases/kernel/io/ltp-aiodio/common.h     | 6 ++++--
>  testcases/kernel/io/ltp-aiodio/dio_sparse.c | 2 +-
>  2 files changed, 5 insertions(+), 3 deletions(-)

> diff --git a/testcases/kernel/io/ltp-aiodio/common.h b/testcases/kernel/io/ltp-aiodio/common.h
> index 9a2d2716661651adf40c635ac516cc70068c9393..d3f05a3c1e75cd4baa629cbce1872729a0d641c6 100644
> --- a/testcases/kernel/io/ltp-aiodio/common.h
> +++ b/testcases/kernel/io/ltp-aiodio/common.h
> @@ -9,6 +9,8 @@
>  #include <stdlib.h>
>  #include "tst_test.h"

> +#define READ_BUFFER_SIZE 4096
> +
>  static inline char *check_zero(char *buf, int size)
>  {
>  	char *p;
> @@ -57,7 +59,7 @@ static inline void io_append(const char *path, char pattern, int flags, size_t b

>  static inline void io_read(const char *filename, int filesize, volatile int *run_child)
>  {
> -	char buff[4096];
> +	char buff[READ_BUFFER_SIZE];
>  	int fd;
>  	int i;
>  	int r;
> @@ -102,7 +104,7 @@ exit:

>  static inline void io_read_eof(const char *filename, volatile int *run_child)
>  {
> -	char buff[4096];
> +	char buff[READ_BUFFER_SIZE];
>  	int fd;
>  	int r;

> diff --git a/testcases/kernel/io/ltp-aiodio/dio_sparse.c b/testcases/kernel/io/ltp-aiodio/dio_sparse.c
> index c87e5ab1aca7c8910f76ee87f86b561f548d4cdf..d858340bf9a707fb019e82c644da7f355ad0effd 100644
> --- a/testcases/kernel/io/ltp-aiodio/dio_sparse.c
> +++ b/testcases/kernel/io/ltp-aiodio/dio_sparse.c
> @@ -32,7 +32,7 @@ static char *str_filesize;
>  static char *str_offset;

>  static int numchildren = 16;
> -static long long writesize = 1024;
> +static long long writesize = READ_BUFFER_SIZE;
>  static long long filesize = 100 * 1024 * 1024;
>  static long long offset = 0;
>  static long long alignment;

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Re: [LTP] [PATCH] io: fix really slow dio_sparse on certain systems

[Andrea Cervesato via ltp]

Hi!

>
> LGTM. IMHO good for a release.
>

Should I merge it with your review tag? I also noticed that I forgot to
update the default value in the test options. I send v2, then we should
merge it if possible because this issue causes test to complete in 4
hours on certain systems.

King regards,

-- 
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com


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Re: [LTP] [PATCH] io: fix really slow dio_sparse on certain systems

[Petr Vorel]

> Hi!


> > LGTM. IMHO good for a release.


> Should I merge it with your review tag? I also noticed that I forgot to
> update the default value in the test options. I send v2, then we should
> merge it if possible because this issue causes test to complete in 4
> hours on certain systems.

+1. Please Cc me, I'll add my RBT in v2.

Kind regards,
Petr

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Re: [LTP] [PATCH] io: fix really slow dio_sparse on certain systems

[Andrea Cervesato via ltp]

On Mon Jan 26, 2026 at 11:07 AM CET, Petr Vorel wrote:
> > Hi!
>
>
> > > LGTM. IMHO good for a release.
>
>
> > Should I merge it with your review tag? I also noticed that I forgot to
> > update the default value in the test options. I send v2, then we should
> > merge it if possible because this issue causes test to complete in 4
> > hours on certain systems.
>
> +1. Please Cc me, I'll add my RBT in v2.
>
> Kind regards,
> Petr


Sorry that was sent already without CC, you can find it in the ML.

-- 
Andrea Cervesato
SUSE QE Automation Engineer Linux
andrea.cervesato@suse.com


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