[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;