[igt-dev] [Intel-gfx] [PATCH i-g-t 1/3] igt/gem_sync: Exercise sync after context switch

[Antonio Argenziano]

On 10/08/18 04:01, Chris Wilson wrote:
> This exercises a special case that may be of interest, waiting for a
> context that may be preempted in order to reduce the wait.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> ---
>   tests/gem_sync.c | 146 +++++++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 146 insertions(+)
> 
> diff --git a/tests/gem_sync.c b/tests/gem_sync.c
> index 493ae61df..495ca3b53 100644
> --- a/tests/gem_sync.c
> +++ b/tests/gem_sync.c
> @@ -409,6 +409,144 @@ store_ring(int fd, unsigned ring, int num_children, int timeout)
>   	igt_assert_eq(intel_detect_and_clear_missed_interrupts(fd), 0);
>   }
>   
> +static void
> +switch_ring(int fd, unsigned ring, int num_children, int timeout)
> +{
> +	const int gen = intel_gen(intel_get_drm_devid(fd));
> +	unsigned engines[16];
> +	const char *names[16];
> +	int num_engines = 0;
> +
> +	gem_require_contexts(fd);
> +
> +	if (ring == ALL_ENGINES) {
> +		for_each_physical_engine(fd, ring) {
> +			if (!gem_can_store_dword(fd, ring))
> +				continue;
> +
> +			names[num_engines] = e__->name;
> +			engines[num_engines++] = ring;
> +			if (num_engines == ARRAY_SIZE(engines))
> +				break;
> +		}
> +
> +		num_children *= num_engines;
> +	} else {
> +		gem_require_ring(fd, ring);
> +		igt_require(gem_can_store_dword(fd, ring));
> +		names[num_engines] = NULL;
> +		engines[num_engines++] = ring;
> +	}
> +
> +	intel_detect_and_clear_missed_interrupts(fd);
> +	igt_fork(child, num_children) {
> +		struct context {
> +			struct drm_i915_gem_exec_object2 object[2];
> +			struct drm_i915_gem_relocation_entry reloc[1024];
> +			struct drm_i915_gem_execbuffer2 execbuf;
> +		} contexts[2];
> +		double start, elapsed;
> +		unsigned long cycles;
> +
> +		for (int i = 0; i < ARRAY_SIZE(contexts); i++) {
> +			const uint32_t bbe = MI_BATCH_BUFFER_END;
> +			const uint32_t sz = 32 << 10;
> +			struct context *c = &contexts[i];
> +			uint32_t *batch, *b;
> +
> +			memset(&c->execbuf, 0, sizeof(c->execbuf));
> +			c->execbuf.buffers_ptr = to_user_pointer(c->object);
> +			c->execbuf.flags = engines[child % num_engines];
> +			c->execbuf.flags |= LOCAL_I915_EXEC_NO_RELOC;
> +			c->execbuf.flags |= LOCAL_I915_EXEC_HANDLE_LUT;
> +			if (gen < 6)
> +				c->execbuf.flags |= I915_EXEC_SECURE;
> +			c->execbuf.rsvd1 = gem_context_create(fd);
> +
> +			memset(c->object, 0, sizeof(c->object));
> +			c->object[0].handle = gem_create(fd, 4096);
> +			gem_write(fd, c->object[0].handle, 0, &bbe, sizeof(bbe));
> +			c->execbuf.buffer_count = 1;
> +			gem_execbuf(fd, &c->execbuf);
> +
> +			c->object[0].flags |= EXEC_OBJECT_WRITE;
> +			c->object[1].handle = gem_create(fd, sz);
> +
> +			c->object[1].relocs_ptr = to_user_pointer(c->reloc);
> +			c->object[1].relocation_count = 1024;
> +
> +			batch = gem_mmap__cpu(fd, c->object[1].handle, 0, sz,
> +					PROT_WRITE | PROT_READ);
> +			gem_set_domain(fd, c->object[1].handle,
> +					I915_GEM_DOMAIN_CPU, I915_GEM_DOMAIN_CPU);
> +
> +			memset(c->reloc, 0, sizeof(c->reloc));
> +			b = batch;
> +			for (int r = 0; r < 1024; r++) {
> +				uint64_t offset;
> +
> +				c->reloc[r].presumed_offset = c->object[0].offset;
> +				c->reloc[r].offset = (b - batch + 1) * sizeof(*batch);
> +				c->reloc[r].delta = r * sizeof(uint32_t);
> +				c->reloc[r].read_domains = I915_GEM_DOMAIN_INSTRUCTION;
> +				c->reloc[r].write_domain = I915_GEM_DOMAIN_INSTRUCTION;
> +
> +				offset = c->object[0].offset + c->reloc[r].delta;
> +				*b++ = MI_STORE_DWORD_IMM | (gen < 6 ? 1 << 22 : 0);
> +				if (gen >= 8) {
> +					*b++ = offset;
> +					*b++ = offset >> 32;
> +				} else if (gen >= 4) {
> +					*b++ = 0;
> +					*b++ = offset;
> +					c->reloc[r].offset += sizeof(*batch);
> +				} else {
> +					b[-1] -= 1;
> +					*b++ = offset;
> +				}
> +				*b++ = r;
> +				*b++ = 0x5 << 23;
> +			}
> +			*b++ = MI_BATCH_BUFFER_END;
> +			igt_assert((b - batch)*sizeof(uint32_t) < sz);
> +			munmap(batch, sz);
> +			c->execbuf.buffer_count = 2;
> +			gem_execbuf(fd, &c->execbuf);
> +			gem_sync(fd, c->object[1].handle);
> +		}
> +
> +		cycles = 0;
> +		elapsed = 0;
> +		start = gettime();
> +		do {
> +			do {
> +				double this;
> +
> +				gem_execbuf(fd, &contexts[0].execbuf);
> +				gem_execbuf(fd, &contexts[1].execbuf);

I'm not sure where the preemption, mentioned in the commit message, is 
coming in.

Antonio

> +
> +				this = gettime();
> +				gem_sync(fd, contexts[1].object[1].handle);
> +				elapsed += gettime() - this;
> +
> +				gem_sync(fd, contexts[0].object[1].handle);
> +			} while (++cycles & 1023);
> +		} while ((gettime() - start) < timeout);
> +		igt_info("%s%sompleted %ld cycles: %.3f us\n",
> +			 names[child % num_engines] ?: "",
> +			 names[child % num_engines] ? " c" : "C",
> +			 cycles, elapsed*1e6/cycles);
> +
> +		for (int i = 0; i < ARRAY_SIZE(contexts); i++) {
> +			gem_close(fd, contexts[i].object[1].handle);
> +			gem_close(fd, contexts[i].object[0].handle);
> +			gem_context_destroy(fd, contexts[i].execbuf.rsvd1);
> +		}
> +	}
> +	igt_waitchildren_timeout(timeout+10, NULL);
> +	igt_assert_eq(intel_detect_and_clear_missed_interrupts(fd), 0);
> +}
> +
>   static void xchg(void *array, unsigned i, unsigned j)
>   {
>   	uint32_t *u32 = array;
> @@ -884,6 +1022,10 @@ igt_main
>   			wakeup_ring(fd, e->exec_id | e->flags, 150, 2);
>   		igt_subtest_f("store-%s", e->name)
>   			store_ring(fd, e->exec_id | e->flags, 1, 150);
> +		igt_subtest_f("switch-%s", e->name)
> +			switch_ring(fd, e->exec_id | e->flags, 1, 150);
> +		igt_subtest_f("forked-switch-%s", e->name)
> +			switch_ring(fd, e->exec_id | e->flags, ncpus, 150);
>   		igt_subtest_f("many-%s", e->name)
>   			store_many(fd, e->exec_id | e->flags, 150);
>   		igt_subtest_f("forked-%s", e->name)
> @@ -898,6 +1040,10 @@ igt_main
>   		store_ring(fd, ALL_ENGINES, 1, 5);
>   	igt_subtest("basic-many-each")
>   		store_many(fd, ALL_ENGINES, 5);
> +	igt_subtest("switch-each")
> +		switch_ring(fd, ALL_ENGINES, 1, 150);
> +	igt_subtest("forked-switch-each")
> +		switch_ring(fd, ALL_ENGINES, ncpus, 150);
>   	igt_subtest("forked-each")
>   		sync_ring(fd, ALL_ENGINES, ncpus, 150);
>   	igt_subtest("forked-store-each")
>