[PATCH 06/10] drm/i915: Choose not to evict faultable objects from the GGTT

Chris Wilson
2016-08-12T10:28:37Z

Often times we do not want to evict mapped objects from the GGTT as
these are quite expensive to teardown and frequently reused (causing an
equally, if not more so, expensive setup). In particular, when faulting
in a new object we want to avoid evicting an active object, or else we
may trigger a page-fault-of-doom as we ping-pong between evicting two
objects.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
---
drivers/gpu/drm/i915/i915_gem.c | 9 +++++----
drivers/gpu/drm/i915/i915_gem_evict.c | 7 +++++--
drivers/gpu/drm/i915/i915_gem_gtt.h | 1 +
3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index a64e8a133cdb..90308b2c4b0f 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1686,6 +1686,7 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf)
struct i915_vma *vma;
pgoff_t page_offset;
unsigned long pfn;
+ unsigned int flags;
int ret;

/* We don't use vmf->pgoff since that has the fake offset */
@@ -1715,10 +1716,10 @@ int i915_gem_fault(struct vm_area_struct *area, struct vm_fault *vmf)
goto err_unlock;
}

- /* Use a partial view if the object is bigger than the aperture. */
- /* Now pin it into the GTT if needed */
- vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
- PIN_MAPPABLE | PIN_NONBLOCK);
+ flags = PIN_MAPPABLE;
+ if (obj->base.size > 2 << 20)
+ flags |= PIN_NONBLOCK | PIN_NOFAULT;
+ vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0, flags);
if (IS_ERR(vma)) {
struct i915_ggtt_view partial;
unsigned int chunk_size;
diff --git a/drivers/gpu/drm/i915/i915_gem_evict.c b/drivers/gpu/drm/i915/i915_gem_evict.c
index f76c06e92677..fde61d7adf4d 100644
--- a/drivers/gpu/drm/i915/i915_gem_evict.c
+++ b/drivers/gpu/drm/i915/i915_gem_evict.c
@@ -47,7 +47,7 @@ gpu_is_idle(struct drm_i915_private *dev_priv)
}

static bool
-mark_free(struct i915_vma *vma, struct list_head *unwind)
+mark_free(struct i915_vma *vma, unsigned int flags, struct list_head *unwind)
{
if (i915_vma_is_pinned(vma))
return false;
@@ -55,6 +55,9 @@ mark_free(struct i915_vma *vma, struct list_head *unwind)
if (WARN_ON(!list_empty(&vma->exec_list)))
return false;

+ if (flags & PIN_NOFAULT && vma->obj->fault_mappable)
+ return false;
+
list_add(&vma->exec_list, unwind);
return drm_mm_scan_add_block(&vma->node);
}
@@ -129,7 +132,7 @@ search_again:
phase = phases;
do {
list_for_each_entry(vma, *phase, vm_link)
- if (mark_free(vma, &eviction_list))
+ if (mark_free(vma, flags, &eviction_list))
goto found;
} while (*++phase);

diff --git a/drivers/gpu/drm/i915/i915_gem_gtt.h b/drivers/gpu/drm/i915/i915_gem_gtt.h
index 4b67347834b5..3d85a1959bd1 100644
--- a/drivers/gpu/drm/i915/i915_gem_gtt.h
+++ b/drivers/gpu/drm/i915/i915_gem_gtt.h
@@ -639,6 +639,7 @@ void i915_gem_gtt_finish_object(struct drm_i915_gem_object *obj);
#define PIN_NONBLOCK BIT(0)
#define PIN_MAPPABLE BIT(1)
#define PIN_ZONE_4G BIT(2)
+#define PIN_NOFAULT BIT(3)

#define PIN_MBZ BIT(5) /* I915_VMA_PIN_OVERFLOW */
#define PIN_GLOBAL BIT(6) /* I915_VMA_GLOBAL_BIND */
--
2.8.1