drm/i915: Avoid evicting user fault mappable vma for pread/pwrite

Both pread/pwrite GTT paths provide a fast fallback in case we cannot
map the whole object at a time. Currently, we use the fallback for very
large objects and for active objects that would require remapping, but
we can also add active fault mappable objects to the list that we want
to avoid evicting. The rationale is that such fault mappable objects are
in active use and to evict requires tearing down the CPU PTE and forcing
a page fault on the next access; more costly, and intefers with other
processes, than our per-page GTT fallback.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20171009084401.29090-6-chris@chris-wilson.co.uk
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 9cb8f85cbaadd8b4cd8f5c7c70b5d7ab392c26e4..6f5c0d6da06afde97825097b3e932f3d3c6af15e 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1055,7 +1055,9 @@ i915_gem_gtt_pread(struct drm_i915_gem_object *obj,
 
        intel_runtime_pm_get(i915);
        vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
-                                      PIN_MAPPABLE | PIN_NONBLOCK);
+                                      PIN_MAPPABLE |
+                                      PIN_NONFAULT |
+                                      PIN_NONBLOCK);
        if (!IS_ERR(vma)) {
                node.start = i915_ggtt_offset(vma);
                node.allocated = false;
@@ -1239,7 +1241,9 @@ i915_gem_gtt_pwrite_fast(struct drm_i915_gem_object *obj,
 
        intel_runtime_pm_get(i915);
        vma = i915_gem_object_ggtt_pin(obj, NULL, 0, 0,
-                                      PIN_MAPPABLE | PIN_NONBLOCK);
+                                      PIN_MAPPABLE |
+                                      PIN_NONFAULT |
+                                      PIN_NONBLOCK);
        if (!IS_ERR(vma)) {
                node.start = i915_ggtt_offset(vma);
                node.allocated = false;