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loader/dri3: Overhaul draw->cur_num_back handling

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draw->cur_num_back is no longer used for immediately reducing the number
of allocated back buffers. It just reflects how many of them are
currently allocated, and is used to prevent allocating more if the
current maximum is already reached.

This fixes an issue where the current in-progress back buffer could get
freed, which would result in visible artifacts.

Unused buffers are freed once they exceed buffer age 200. This ensures
we do not keep around more buffers than necessary in the long run.

v2:
* Drop buffer age threshold to 200. This will free unused buffers more
  quickly, and seems enough to avoid doing so prematurely even with
  "glxgears -fullscreen" running at thousands of frames per second.
* Use "buf_id != LOADER_DRI3_FRONT_ID". (Pierre-Eric Pelloux-Prayer)
* Simplify loader_dri3_get_buffers changes slightly.
* We can now use any unallocated back buffer slot in dri3_find_back.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/20385>
This commit is contained in:
Michel Dänzer 2022-12-19 12:25:46 +01:00 • committed by Marge Bot
parent 27366cb510
commit 25a151533c
1 changed files with 26 additions and 35 deletions
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61
src/loader/loader_dri3_helper.c
View file

@ -271,26 +271,12 @@ dri3_update_max_num_back(struct loader_dri3_drawable *draw)
{
switch (draw->last_present_mode) {
case XCB_PRESENT_COMPLETE_MODE_FLIP: {
int new_max;
if (draw->swap_interval == 0)
new_max = 4;
draw->max_num_back = 4;
else
new_max = 3;
assert(new_max <= LOADER_DRI3_MAX_BACK);
if (new_max != draw->max_num_back) {
/* On transition from swap interval == 0 to != 0, start with two
* buffers again. Otherwise keep the current number of buffers. Either
* way, more will be allocated if needed.
*/
if (new_max < draw->max_num_back)
draw->cur_num_back = 2;
draw->max_num_back = new_max;
}
draw->max_num_back = 3;
assert(draw->max_num_back <= LOADER_DRI3_MAX_BACK);
break;
}
@ -298,12 +284,6 @@ dri3_update_max_num_back(struct loader_dri3_drawable *draw)
break;
default:
/* On transition from flips to copies, start with a single buffer again,
* a second one will be allocated if needed
*/
if (draw->max_num_back != 2)
draw->cur_num_back = 1;
draw->max_num_back = 2;
}
}
@ -332,6 +312,9 @@ static void
dri3_set_render_buffer(struct loader_dri3_drawable *draw, int buf_id,
struct loader_dri3_buffer *buffer)
{
if (buf_id != LOADER_DRI3_FRONT_ID && !draw->buffers[buf_id])
draw->cur_num_back++;
draw->buffers[buf_id] = buffer;
}
@ -359,6 +342,9 @@ dri3_free_render_buffer(struct loader_dri3_drawable *draw,
free(buffer);
draw->buffers[buf_id] = NULL;
if (buf_id != LOADER_DRI3_FRONT_ID)
draw->cur_num_back--;
}
void
@ -721,7 +707,7 @@ dri3_find_back(struct loader_dri3_drawable *draw, bool prefer_a_different)
max_num = 1;
draw->cur_blit_source = -1;
} else {
max_num = draw->max_num_back;
max_num = LOADER_DRI3_MAX_BACK;
}
/* In a DRI_PRIME situation, if prefer_a_different is true, we first try
@ -735,9 +721,9 @@ dri3_find_back(struct loader_dri3_drawable *draw, bool prefer_a_different)
*/
int current_back_id = draw->cur_back;
do {
/* Find idle buffer with lowest buffer age, or first unallocated slot */
/* Find idle buffer with lowest buffer age, or an unallocated slot */
for (b = 0; b < max_num; b++) {
int id = LOADER_DRI3_BACK_ID((b + draw->cur_back) % draw->max_num_back);
int id = LOADER_DRI3_BACK_ID((b + current_back_id) % LOADER_DRI3_MAX_BACK);
buffer = draw->buffers[id];
if (buffer) {
@ -747,7 +733,8 @@ dri3_find_back(struct loader_dri3_drawable *draw, bool prefer_a_different)
best_id = id;
best_swap = buffer->last_swap;
}
} else if (best_id == -1 || (!best_swap && id < best_id)) {
} else if (best_id == -1 &&
draw->cur_num_back < draw->max_num_back) {
best_id = id;
}
}
@ -758,10 +745,8 @@ dri3_find_back(struct loader_dri3_drawable *draw, bool prefer_a_different)
best_id = current_back_id;
} while (best_id == -1 && dri3_wait_for_event_locked(draw, NULL));
if (best_id != -1) {
if (best_id != -1)
draw->cur_back = best_id;
draw->cur_num_back = MAX2(draw->cur_num_back, best_id + 1);
}
unlock:
mtx_unlock(&draw->mtx);
@ -2256,17 +2241,21 @@ loader_dri3_get_buffers(__DRIdrawable *driDrawable,
buffers->front = NULL;
buffers->back = NULL;
front = NULL;
back = NULL;
if (!dri3_update_drawable(draw))
return false;
dri3_update_max_num_back(draw);
/* Free no longer needed back buffers */
for (buf_id = draw->cur_num_back; buf_id < LOADER_DRI3_MAX_BACK; buf_id++) {
if (draw->cur_blit_source != buf_id)
for (buf_id = 0; buf_id < LOADER_DRI3_MAX_BACK; buf_id++) {
int buffer_age;
back = draw->buffers[buf_id];
if (!back || !back->last_swap || draw->cur_blit_source == buf_id)
continue;
buffer_age = draw->send_sbc - back->last_swap + 1;
if (buffer_age > 200)
dri3_free_render_buffer(draw, buf_id);
}
@ -2302,6 +2291,7 @@ loader_dri3_get_buffers(__DRIdrawable *driDrawable,
} else {
dri3_free_buffers(driDrawable, loader_dri3_buffer_front, draw);
draw->have_fake_front = 0;
front = NULL;
}
if (buffer_mask & __DRI_IMAGE_BUFFER_BACK) {
@ -2315,6 +2305,7 @@ loader_dri3_get_buffers(__DRIdrawable *driDrawable,
} else {
dri3_free_buffers(driDrawable, loader_dri3_buffer_back, draw);
draw->have_back = 0;
back = NULL;
}
if (front) {