venus: add vn_renderer_shmem_pool

It provides shmem suballocations.  It is designed to be used with
short-lived shmems.  A long-lived shmem can hold on to some large
allocation while only using a likely small region of the large
allocation.

v2: cleanups suggested by Yiwei

Signed-off-by: Chia-I Wu <olvaffe@gmail.com>
Reviewed-by: Ryan Neph <ryanneph@google.com> (v1)
Reviewed-by: Yiwei Zhang <zzyiwei@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14179>

src/virtio/vulkan/vn_renderer_util.c

@@ -43,3 +43,71 @@ vn_renderer_submit_simple_sync(struct vn_renderer *renderer,
 
    return result;
 }
+
+void
+vn_renderer_shmem_pool_init(UNUSED struct vn_renderer *renderer,
+                            struct vn_renderer_shmem_pool *pool,
+                            size_t min_alloc_size)
+{
+   *pool = (struct vn_renderer_shmem_pool){
+      /* power-of-two to hit shmem cache */
+      .min_alloc_size = util_next_power_of_two(min_alloc_size),
+   };
+}
+
+void
+vn_renderer_shmem_pool_fini(struct vn_renderer *renderer,
+                            struct vn_renderer_shmem_pool *pool)
+{
+   if (pool->shmem)
+      vn_renderer_shmem_unref(renderer, pool->shmem);
+}
+
+static bool
+vn_renderer_shmem_pool_grow(struct vn_renderer *renderer,
+                            struct vn_renderer_shmem_pool *pool,
+                            size_t size)
+{
+   /* power-of-two to hit shmem cache */
+   size_t alloc_size = pool->min_alloc_size;
+   while (alloc_size < size) {
+      alloc_size <<= 1;
+      if (!alloc_size)
+         return false;
+   }
+
+   struct vn_renderer_shmem *shmem =
+      vn_renderer_shmem_create(renderer, alloc_size);
+   if (!shmem)
+      return false;
+
+   if (pool->shmem)
+      vn_renderer_shmem_unref(renderer, pool->shmem);
+
+   pool->shmem = shmem;
+   pool->size = alloc_size;
+   pool->used = 0;
+
+   return true;
+}
+
+struct vn_renderer_shmem *
+vn_renderer_shmem_pool_alloc(struct vn_renderer *renderer,
+                             struct vn_renderer_shmem_pool *pool,
+                             size_t size,
+                             size_t *out_offset)
+{
+   if (unlikely(size > pool->size - pool->used)) {
+      if (!vn_renderer_shmem_pool_grow(renderer, pool, size))
+         return NULL;
+
+      assert(size <= pool->size - pool->used);
+   }
+
+   struct vn_renderer_shmem *shmem =
+      vn_renderer_shmem_ref(renderer, pool->shmem);
+   *out_offset = pool->used;
+   pool->used += size;
+
+   return shmem;
+}

src/virtio/vulkan/vn_renderer_util.h

@@ -8,6 +8,15 @@
 
 #include "vn_renderer.h"
 
+/* for suballocations of short-lived shmems, not thread-safe */
+struct vn_renderer_shmem_pool {
+   size_t min_alloc_size;
+
+   struct vn_renderer_shmem *shmem;
+   size_t size;
+   size_t used;
+};
+
 static inline VkResult
 vn_renderer_submit_simple(struct vn_renderer *renderer,
                           const void *cs_data,
@@ -29,4 +38,19 @@ vn_renderer_submit_simple_sync(struct vn_renderer *renderer,
                                const void *cs_data,
                                size_t cs_size);
 
+void
+vn_renderer_shmem_pool_init(struct vn_renderer *renderer,
+                            struct vn_renderer_shmem_pool *pool,
+                            size_t min_alloc_size);
+
+void
+vn_renderer_shmem_pool_fini(struct vn_renderer *renderer,
+                            struct vn_renderer_shmem_pool *pool);
+
+struct vn_renderer_shmem *
+vn_renderer_shmem_pool_alloc(struct vn_renderer *renderer,
+                             struct vn_renderer_shmem_pool *pool,
+                             size_t size,
+                             size_t *out_offset);
+
 #endif /* VN_RENDERER_UTIL_H */