Measure the baseline latency between contexts in order to directly compare that with the additional cost of preemption.
Signed-off-by: Chris Wilson <[email protected]> --- tests/i915/gem_exec_latency.c | 118 ++++++++++++++++++++++++++++++++++ 1 file changed, 118 insertions(+) diff --git a/tests/i915/gem_exec_latency.c b/tests/i915/gem_exec_latency.c index 6dd191ece..b3ec34516 100644 --- a/tests/i915/gem_exec_latency.c +++ b/tests/i915/gem_exec_latency.c @@ -628,6 +628,115 @@ rthog_latency_on_ring(int fd, unsigned int engine, const char *name, unsigned in munmap(results, MMAP_SZ); } +static void context_switch(int i915, + unsigned int engine, const char *name, + unsigned int flags) +{ + struct drm_i915_gem_exec_object2 obj[2]; + struct drm_i915_gem_relocation_entry reloc[5]; + struct drm_i915_gem_execbuffer2 eb; + uint32_t *cs, *bbe, *results, v; + struct igt_mean mean; + uint32_t ctx[2]; + + for (int i = 0; i < ARRAY_SIZE(ctx); i++) + ctx[i] = gem_context_create(i915); + + if (flags & PREEMPT) { + gem_context_set_priority(i915, ctx[0], -1023); + gem_context_set_priority(i915, ctx[1], +1023); + } + + memset(obj, 0, sizeof(obj)); + obj[0].handle = gem_create(i915, 4096); + gem_set_caching(i915, obj[0].handle, 1); + results = gem_mmap__cpu(i915, obj[0].handle, 0, 4096, PROT_READ); + gem_set_domain(i915, obj[0].handle, I915_GEM_DOMAIN_CPU, 0); + + obj[1].handle = gem_create(i915, 4096); + memset(reloc,0, sizeof(reloc)); + obj[1].relocation_count = ARRAY_SIZE(reloc); + obj[1].relocs_ptr = to_user_pointer(reloc); + bbe = gem_mmap__wc(i915, obj[1].handle, 0, 4096, PROT_WRITE); + gem_set_domain(i915, obj[1].handle, + I915_GEM_DOMAIN_WC, I915_GEM_DOMAIN_WC); + + cs = bbe; + *cs++ = 0x5 << 23; + *cs++ = 0x24 << 23 | 2; /* SRM */ + *cs++ = RCS_TIMESTAMP; /* ring local! */ + reloc[0].target_handle = obj[0].handle; + reloc[0].offset = (cs - bbe) * sizeof(*cs); + *cs++ = 0; + *cs++ = 0; + *cs++ = MI_BATCH_BUFFER_START | 1; + reloc[1].target_handle = obj[1].handle; + reloc[1].offset = (cs - bbe) * sizeof(*cs); + *cs++ = 0; + *cs++ = 0; + + cs = bbe + 64; + *cs++ = 0x24 << 23 | 2; /* SRM */ + *cs++ = RCS_TIMESTAMP; /* ring local! */ + reloc[2].target_handle = obj[0].handle; + reloc[2].offset = (cs - bbe) * sizeof(*cs); + *cs++ = reloc[2].delta = 4; + *cs++ = 0; + *cs++ = 0x29 << 23 | 2; /* LRM */ + *cs++ = 0x2600; /* CS_GPR */ + reloc[3].target_handle = obj[0].handle; + reloc[3].offset = (cs - bbe) * sizeof(*cs); + *cs++ = 0; + *cs++ = 0; + *cs++ = 0x24 << 23 | 2; /* SRM */ + *cs++ = 0x2600; /* CS_GPR */ + reloc[4].target_handle = obj[0].handle; + reloc[4].offset = (cs - bbe) * sizeof(*cs); + *cs++ = reloc[4].delta = 8; + *cs++ = 0; + *cs++ = 0xa << 23; + + memset(&eb, 0, sizeof(eb)); + eb.buffers_ptr = to_user_pointer(obj); + eb.buffer_count = ARRAY_SIZE(obj); + eb.flags = engine; + eb.flags |= LOCAL_I915_EXEC_NO_RELOC; + + v = 0; + igt_mean_init(&mean); + igt_until_timeout(5) { + eb.rsvd1 = ctx[0]; + eb.batch_start_offset = 0; + gem_execbuf(i915, &eb); + + while (results[0] == v) + igt_assert(gem_bo_busy(i915, obj[1].handle)); + + eb.rsvd1 = ctx[1]; + eb.batch_start_offset = 64 * sizeof(*cs); + gem_execbuf(i915, &eb); + + *bbe = 0xa << 23; + gem_sync(i915, obj[1].handle); + *bbe = 0x5 << 23; + + v = results[0]; + igt_mean_add(&mean, (results[1] - results[2]) * rcs_clock); + } + igt_info("%s context switch latency%s: %.2f±%.2fus\n", + name, flags & PREEMPT ? " (preempt)" : "", + 1e-3 * igt_mean_get(&mean), + 1e-3 * sqrt(igt_mean_get_variance(&mean))); + munmap(results, 4096); + munmap(bbe, 4096); + + for (int i = 0; i < ARRAY_SIZE(obj); i++) + gem_close(i915, obj[i].handle); + + for (int i = 0; i < ARRAY_SIZE(ctx); i++) + gem_context_destroy(i915, ctx[i]); +} + static double clockrate(int i915, int reg) { volatile uint32_t *mmio; @@ -753,12 +862,21 @@ igt_main e->exec_id | e->flags, e->name, CORK); + igt_subtest_f("%s-cs", e->name) + context_switch(device, + e->exec_id | e->flags, + e->name, 0); igt_subtest_group { igt_fixture { gem_require_contexts(device); igt_require(gem_scheduler_has_preemption(device)); } + igt_subtest_f("%s-cs-preempt", e->name) + context_switch(device, + e->exec_id | e->flags, + e->name, PREEMPT); + igt_subtest_f("%s-preemption", e->name) latency_from_ring(device, e->exec_id | e->flags, -- 2.20.1 _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
