Re: [PATCH i-g-t] tests/gem_mmap_gtt: add huge BO test

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

Hi,

On 04/07/2015 01:23 PM, Joonas Lahtinen wrote:
> Add a straightforward test that allocates a BO that is bigger than
> (by 1 page currently) the mappable aperture, tests mmap access to it
> by CPU directly and through GTT in sequence.
>
> Currently it is expected for the GTT access to gracefully fail as
> all objects are attempted to get pinned to GTT completely for mmap
> access. Once the partial view support is merged to kernel, the test
> should pass for all parts.
>
> Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> ---
>   tests/gem_mmap_gtt.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 68 insertions(+)
>
> diff --git a/tests/gem_mmap_gtt.c b/tests/gem_mmap_gtt.c
> index 55c66a2..bf3627c 100644
> --- a/tests/gem_mmap_gtt.c
> +++ b/tests/gem_mmap_gtt.c
> @@ -41,6 +41,10 @@
>   #include "drmtest.h"
>   #include "igt_debugfs.h"
>
> +#ifndef PAGE_SIZE
> +#define PAGE_SIZE 4096
> +#endif
> +
>   static int OBJECT_SIZE = 16*1024*1024;
>
>   static void set_domain(int fd, uint32_t handle)
> @@ -258,6 +262,68 @@ test_write_gtt(int fd)
>   }
>
>   static void
> +test_huge_bo(int fd)
> +{
> +	uint32_t bo;
> +	char *ptr_cpu;
> +	char *ptr_gtt;
> +	char *cpu_pattern;
> +	uint64_t mappable_aperture_pages = gem_mappable_aperture_size() /
> +					   PAGE_SIZE;
> +	uint64_t huge_object_size = (mappable_aperture_pages + 1) * PAGE_SIZE;
> +	uint64_t last_offset = huge_object_size - PAGE_SIZE;
> +
> +	cpu_pattern = malloc(PAGE_SIZE);
> +	igt_assert(cpu_pattern);

I'd be tempted to use 4k from the stack for simplicity.

> +	memset(cpu_pattern, 0xaa, PAGE_SIZE);
> +
> +	bo = gem_create(fd, huge_object_size);
> +
> +	ptr_cpu = gem_mmap__cpu(fd, bo, 0, huge_object_size,
> +				PROT_READ | PROT_WRITE);
> +	if (!ptr_cpu) {
> +		igt_warn("Not enough free memory for huge BO test!\n");
> +		goto out;

Free address space or free memory?

Also, igt_require so test skips in that case?

> +	}
> +
> +	/* Test read/write to first/last page with CPU. */
> +	memcpy(ptr_cpu, cpu_pattern, PAGE_SIZE);
> +	igt_assert(memcmp(ptr_cpu, cpu_pattern, PAGE_SIZE) == 0);
> +
> +	memcpy(ptr_cpu + last_offset, cpu_pattern, PAGE_SIZE);
> +	igt_assert(memcmp(ptr_cpu + last_offset, cpu_pattern, PAGE_SIZE) == 0);
> +
> +	igt_assert(memcmp(ptr_cpu, ptr_cpu + last_offset, PAGE_SIZE) == 0);
> +
> +	munmap(ptr_cpu, huge_object_size);
> +	ptr_cpu = NULL;
> +
> +	ptr_gtt = gem_mmap__gtt(fd, bo, huge_object_size,
> +			        PROT_READ | PROT_WRITE);
> +	if (!ptr_gtt) {
> +		igt_debug("Huge BO GTT mapping not supported!\n");
> +		goto out;

igt_require as above? Hm, although ideally test would be able to detect 
the feature (once it is added to the kernel) so it could assert here.

> +	}
> +
> +	/* Test read/write to first/last page through GTT. */
> +	set_domain(fd, bo);
> +
> +	igt_assert(memcmp(ptr_gtt, cpu_pattern, PAGE_SIZE) == 0);
> +	igt_assert(memcmp(ptr_gtt + last_offset, cpu_pattern, PAGE_SIZE) == 0);
> +
> +	memset(ptr_gtt, 0x55, PAGE_SIZE);
> +	igt_assert(memcmp(ptr_gtt + last_offset, cpu_pattern, PAGE_SIZE) == 0);
> +
> +	memset(ptr_gtt + last_offset, 0x55, PAGE_SIZE);
> +	igt_assert(memcmp(ptr_gtt, ptr_gtt + last_offset, PAGE_SIZE) == 0);

Comments for the above would be nice just to explain what is being 
tested and how.

Won't the last test has side effects with partial views since it is 
accessing beginning and end of the object? Would it be better to memcmp 
against a pattern on stack or in heap like cpu_pattern?

Will you support two simultaneous partial views or the last memcmp will 
cause a lot of partial view creation/destruction?

> +
> +	munmap(ptr_gtt, huge_object_size);
> +out:
> +	gem_close(fd, bo);
> +	free(cpu_pattern);
> +}
> +
> +static void
>   test_read(int fd)
>   {
>   	void *dst;
> @@ -395,6 +461,8 @@ igt_main
>   		run_without_prefault(fd, test_write_gtt);
>   	igt_subtest("write-cpu-read-gtt")
>   		test_write_cpu_read_gtt(fd);
> +	igt_subtest("huge-bo")
> +		test_huge_bo(fd);
>
>   	igt_fixture
>   		close(fd);
>

Regards,

Tvrtko
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