Re: [PATCH v2 02/12] queuelat: Use clock syscall for ARM 32 bit

[John Kacur <jkacur@redhat.com>]

On Wed, 5 Jun 2019, Daniel Wagner wrote:

> CPUs such as Cortex-M8 don't have a rdtsc instruction. Fallback using
> a syscall.
> 
> Signed-off-by: Daniel Wagner <wagi@monom.org>
> ---
>  src/queuelat/queuelat.c | 31 ++++++++++++++++++++++++++-----
>  1 file changed, 26 insertions(+), 5 deletions(-)
> 
> diff --git a/src/queuelat/queuelat.c b/src/queuelat/queuelat.c
> index 3b291f168768..a5525e41776a 100644
> --- a/src/queuelat/queuelat.c
> +++ b/src/queuelat/queuelat.c
> @@ -7,6 +7,7 @@
>  #include <stdio.h>
>  #include <unistd.h>
>  #include <signal.h>
> +#include <time.h>
>  
>  #define NSEC_PER_SEC 1000000000
>  
> @@ -249,6 +250,8 @@ typedef unsigned long long cycles_t;
>  typedef unsigned long long usecs_t;
>  typedef unsigned long long u64;
>  
> +#if defined __x86_64__ || defined __i386__
> +
>  #ifdef __x86_64__
>  #define DECLARE_ARGS(val, low, high)    unsigned low, high
>  #define EAX_EDX_VAL(val, low, high)     ((low) | ((u64)(high) << 32))
> @@ -270,7 +273,25 @@ static inline unsigned long long __rdtscll(void)
>          return EAX_EDX_VAL(val, low, high);
>  }
>  
> -#define rdtscll(val) do { (val) = __rdtscll(); } while (0)
> +#define gettick(val) do { (val) = __rdtscll(); } while (0)
> +
> +#elif defined __arm__
> +
> +static inline unsigned long long __clock_gettime(void)
> +{
> +	struct timespec now;
> +	int ret;
> +
> +	ret = clock_gettime(CLOCK_MONOTONIC, &now);
> +	if (ret < 0)
> +		return 0;
> +
> +	return now.tv_nsec;
> +}
> +
> +#define gettick(val) do { (val) = __clock_gettime(); } while (0)
> +
> +#endif
>  
>  static void init_buckets(void)
>  {
> @@ -348,9 +369,9 @@ static void run_n(int n)
>  
>  	memmove(dest, src, n);
>  	for (i = 0; i < loops; i++) {
> -		rdtscll(b);
> +		gettick(b);
>  		memmove(dest, src, n);
> -		rdtscll(a);
> +		gettick(a);
>  		delta = (a - b) * cycles_to_ns;
>  		account(delta);
>  	}
> @@ -446,9 +467,9 @@ void main_loop(void)
>  		int ret;
>  		int nr_packets_fill;
>  
> -		rdtscll(b);
> +		gettick(b);
>  		memmove(dest, src, default_n);
> -		rdtscll(a);
> +		gettick(a);
>  		delta = (a - b) * cycles_to_ns;
>  		account(delta);
>  
> -- 

Signed-off-by: John Kacur <jkacur@redhat.com>