intel: Leak the userptr test bo

In order to use userptr, the kernel tracks the owner's mm with a
mmu_notifier. Setting that is very expensive - it involves taking all
mm_locks and a stop_machine(). This tracking lives only for as long as
the client is using userptr objects - so if the client allocates then
frees a userptr in a loop, we will be executing that heavyweight setup
everytime. To ammoritize this cost, just leak the test bo and the single
backing page we use for detecting userptr.

v2: Free the object and memory when bufmgr is destroyed.

Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>

diff --git a/intel/intel_bufmgr_gem.c b/intel/intel_bufmgr_gem.c
index 7c94786..60c06fc 100644 (file)
--- a/intel/intel_bufmgr_gem.c
+++ b/intel/intel_bufmgr_gem.c
@@ -132,6 +132,11 @@ typedef struct _drm_intel_bufmgr_gem {
        unsigned int has_vebox : 1;
        bool fenced_relocs;
 
+       struct {
+               void *ptr;
+               uint32_t handle;
+       } userptr_active;
+
        char *aub_filename;
        FILE *aub_file;
        uint32_t aub_offset;
@@ -943,7 +948,6 @@ has_userptr(drm_intel_bufmgr_gem *bufmgr_gem)
        void *ptr;
        long pgsz;
        struct drm_i915_gem_userptr userptr;
-       struct drm_gem_close close_bo;
 
        pgsz = sysconf(_SC_PAGESIZE);
        assert(pgsz > 0);
@@ -970,15 +974,15 @@ retry:
                return false;
        }
 
-       memclear(close_bo);
-       close_bo.handle = userptr.handle;
-       ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_GEM_CLOSE, &close_bo);
-       free(ptr);
-       if (ret) {
-               fprintf(stderr, "Failed to release test userptr object! (%d) "
-                               "i915 kernel driver may not be sane!\n", errno);
-               return false;
-       }
+       /* We don't release the userptr bo here as we want to keep the
+        * kernel mm tracking alive for our lifetime. The first time we
+        * create a userptr object the kernel has to install a mmu_notifer
+        * which is a heavyweight operation (e.g. it requires taking all
+        * mm_locks and stop_machine()).
+        */
+
+       bufmgr_gem->userptr_active.ptr = ptr;
+       bufmgr_gem->userptr_active.handle = userptr.handle;
 
        return true;
 }
@@ -1805,7 +1809,8 @@ static void
 drm_intel_bufmgr_gem_destroy(drm_intel_bufmgr *bufmgr)
 {
        drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *) bufmgr;
-       int i;
+       struct drm_gem_close close_bo;
+       int i, ret;
 
        free(bufmgr_gem->exec2_objects);
        free(bufmgr_gem->exec_objects);
@@ -1829,6 +1834,18 @@ drm_intel_bufmgr_gem_destroy(drm_intel_bufmgr *bufmgr)
                }
        }
 
+       /* Release userptr bo kept hanging around for optimisation. */
+       if (bufmgr_gem->userptr_active.ptr) {
+               memclear(close_bo);
+               close_bo.handle = bufmgr_gem->userptr_active.handle;
+               ret = drmIoctl(bufmgr_gem->fd, DRM_IOCTL_GEM_CLOSE, &close_bo);
+               free(bufmgr_gem->userptr_active.ptr);
+               if (ret)
+                       fprintf(stderr,
+                               "Failed to release test userptr object! (%d) "
+                               "i915 kernel driver may not be sane!\n", errno);
+       }
+
        free(bufmgr);
 }