Re: [PATCH i-g-t 4/5] benchmarks/gem_exec_trace: use hars_petruska_f54_1_random() from lib/rand

[Jani Nikula <jani.nikula@intel.com>]

On Fri, 19 Jun 2026, Zbigniew Kempczyński <zbigniew.kempczynski@intel.com> wrote:
> On Thu, Jun 18, 2026 at 05:09:52PM +0300, Jani Nikula wrote:
>> Remove the local duplicate of hars_petruska_f54_1_random() by switching
>> to use lib/rand.
>> 
>> Signed-off-by: Jani Nikula <jani.nikula@intel.com>
>> ---
>>  benchmarks/gem_exec_trace.c | 12 +++---------
>>  1 file changed, 3 insertions(+), 9 deletions(-)
>> 
>> diff --git a/benchmarks/gem_exec_trace.c b/benchmarks/gem_exec_trace.c
>> index 4263ccb03dbd..c27639105903 100644
>> --- a/benchmarks/gem_exec_trace.c
>> +++ b/benchmarks/gem_exec_trace.c
>> @@ -42,6 +42,7 @@
>>  #include "drm.h"
>>  #include "drmtest.h"
>>  #include "i915/gem_create.h"
>> +#include "igt_rand.h"
>>  #include "igt_stats.h"
>>  #include "intel_io.h"
>>  #include "ioctl_wrappers.h"
>> @@ -92,14 +93,7 @@ struct trace_wait {
>>  	uint32_t handle;
>>  } __attribute__((packed));
>>  
>> -static uint32_t hars_petruska_f54_1_random(void)
>> -{
>> -	static uint32_t state = 0x12345678;
>> -
>> -#define rol(x,k) ((x << k) | (x >> (32-k)))
>> -	return state = (state ^ rol (state, 5) ^ rol (state, 24)) + 0x37798849;
>> -#undef rol
>> -}
>> +static uint32_t random_state = 0x12345678;
>>  
>>  static double elapsed(const struct timespec *start, const struct timespec *end)
>>  {
>> @@ -277,7 +271,7 @@ static double replay(const char *filename, long nop, long range)
>>  				sizeof(*exec_objects)))->handle = bo[0];
>>  
>>  			if (nop > 0) {
>> -				eb.batch_start_offset = hars_petruska_f54_1_random();
>> +				eb.batch_start_offset = hars_petruska_f54_1_random(&random_state);
>
> With random_state as above this offset is not random. I think adding nop
> to random_state would do this.

I'm only aiming to do a non-functional conversion to existing library
functions. Please explain how this patch changes behaviour; I don't see
it.


BR,
Jani.

>
> --
> Zbigniew
>
>>  				eb.batch_start_offset =
>>  					((uint64_t)eb.batch_start_offset * range) >> 32;
>>  				eb.batch_start_offset = ALIGN(eb.batch_start_offset, 64);
>> -- 
>> 2.47.3
>> 

-- 
Jani Nikula, Intel