Re: [RFC i-g-t] tests/gem_exec_pad_to_size: Test object padding at execbuf

[Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>]

On 03/25/2015 02:28 PM, Chris Wilson wrote:
> On Wed, Mar 25, 2015 at 02:21:00PM +0000, Tvrtko Ursulin wrote:
>> From: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
>>
>> This tests the new EXEC_OBJECT_PAD_TO_SIZE exec_object2 flag.
>>
>> It uses the fact DRM allocation policy is set as ABI and allocates
>> space in order.
>
> Ssh. That's not what I meant to say. I meant that the policy is not ABI,
> and we abuse our internal knowledge to get a working test, as we do
> elsewhere in igt.

Ah, OK. :)

>> That means that we should be able to easily get
>> two bos mapped at adjacent GTT addresses and then test that the
>> pad to size flag will move them apart.
>
>> +	/* Try to get two buffer object next to each other in GTT space. */
>> +	for (try = 0, idx = 0; try < max_tries;) {
>> +		eb_handles[0] = handles[0];
>> +		eb_handles[1] = loc_handles[idx];
>> +		eb_handles[2] = loc_handles[idx + 1];
>> +
>> +		igt_assert(exec(fd, eb_handles, (uint32_t[2]){0, 0},
>> +				offsets) == 0);
>> +
>> +		if (offsets[1] > offsets[0]) {
>> +			distance = offsets[1] - offsets[0];
>> +			if (distance == PAGE_SIZE)
>> +				neighbours = true;
>> +			pad_to_size[0] = ALIGN(distance + PAGE_SIZE, PAGE_SIZE);
>> +		} else {
>> +			distance = offsets[0] - offsets[1];
>> +			if (distance == PAGE_SIZE)
>> +				neighbours = true;
>> +			pad_to_size[1] = ALIGN(distance + PAGE_SIZE, PAGE_SIZE);
>> +		}
>> +
>> +		if (neighbours)
>> +			break;
>
> What's important to make this trick work is to allocate new handles
> every time. That way we fill up the GTT and thereby hope to skip over
> the fragmented part.

It does do that!

Only perhaps I need to make sure they are kept bound so maybe keep them 
mapped or something while trying new ones?

Regards,

Tvrtko




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