[Mesa-dev] [PATCH 2/2] panfrost: Add madvise support to BO cache

[Rob Herring]

The kernel now supports madvise ioctl to indicate which BOs can be freed
when there is memory pressure. Mark BOs purgeable when they are in the
BO cache. The BOs must also be munmapped when they are in the cache or
they cannot be purged.

We could optimize avoiding the madvise ioctl on older kernels once the
driver version bump lands, but probably not worth it given the other
driver features also being added.

Signed-off-by: Rob Herring <robh at kernel.org>
---
 src/gallium/drivers/panfrost/pan_bo_cache.c | 21 +++++++++++++++++++++
 src/gallium/drivers/panfrost/pan_drm.c      |  4 ++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/gallium/drivers/panfrost/pan_bo_cache.c b/src/gallium/drivers/panfrost/pan_bo_cache.c
index 7378d0a8abea..239ea0b46cb2 100644
--- a/src/gallium/drivers/panfrost/pan_bo_cache.c
+++ b/src/gallium/drivers/panfrost/pan_bo_cache.c
@@ -23,6 +23,8 @@
  * Authors (Collabora):
  *   Alyssa Rosenzweig <alyssa.rosenzweig at collabora.com>
  */
+#include <xf86drm.h>
+#include "drm-uapi/panfrost_drm.h"
 
 #include "pan_screen.h"
 #include "util/u_math.h"
@@ -88,9 +90,21 @@ panfrost_bo_cache_fetch(
         list_for_each_entry_safe(struct panfrost_bo, entry, bucket, link) {
                 if (entry->size >= size &&
                     entry->flags == flags) {
+                        int ret;
+                        struct drm_panfrost_madvise madv;
+
                         /* This one works, splice it out of the cache */
                         list_del(&entry->link);
 
+                        madv.handle = entry->gem_handle;
+                        madv.madv = PANFROST_MADV_WILLNEED;
+			madv.retained = 0;
+
+                        ret = drmIoctl(screen->fd, DRM_IOCTL_PANFROST_MADVISE, &madv);
+			if (!ret && !madv.retained) {
+				panfrost_drm_release_bo(screen, entry, false);
+				continue;
+			}
                         /* Let's go! */
                         return entry;
                 }
@@ -109,6 +123,13 @@ panfrost_bo_cache_put(
                 struct panfrost_bo *bo)
 {
         struct list_head *bucket = pan_bucket(screen, bo->size);
+        struct drm_panfrost_madvise madv;
+
+        madv.handle = bo->gem_handle;
+        madv.madv = PANFROST_MADV_DONTNEED;
+	madv.retained = 0;
+
+        drmIoctl(screen->fd, DRM_IOCTL_PANFROST_MADVISE, &madv);
 
         /* Add us to the bucket */
         list_addtail(&bo->link, bucket);
diff --git a/src/gallium/drivers/panfrost/pan_drm.c b/src/gallium/drivers/panfrost/pan_drm.c
index 36a6b975680a..28a4287202bd 100644
--- a/src/gallium/drivers/panfrost/pan_drm.c
+++ b/src/gallium/drivers/panfrost/pan_drm.c
@@ -163,6 +163,8 @@ panfrost_drm_release_bo(struct panfrost_screen *screen, struct panfrost_bo *bo,
         /* Rather than freeing the BO now, we'll cache the BO for later
          * allocations if we're allowed to */
 
+        panfrost_drm_munmap_bo(screen, bo);
+
         if (cacheable) {
                 bool cached = panfrost_bo_cache_put(screen, bo);
 
@@ -172,8 +174,6 @@ panfrost_drm_release_bo(struct panfrost_screen *screen, struct panfrost_bo *bo,
 
         /* Otherwise, if the BO wasn't cached, we'll legitimately free the BO */
 
-        panfrost_drm_munmap_bo(screen, bo);
-
         ret = drmIoctl(screen->fd, DRM_IOCTL_GEM_CLOSE, &gem_close);
         if (ret) {
                 fprintf(stderr, "DRM_IOCTL_GEM_CLOSE failed: %m\n");
-- 
2.20.1