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vulkan/wsi/wayland: Use X11-style image count strategy when using FIFO.

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This is required, otherwise we regress latency in cases where
applications are using FIFO without explicit KHR_present_wait.
This is an unacceptable regression.

The fix is to normalize the behavior to X11 WSI.

Signed-off-by: Hans-Kristian Arntzen <post@arntzen-software.no>
Fixes: d052b0201e ("vulkan/wsi/wayland: Use fifo protocol for FIFO")
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/32029>
This commit is contained in:
Hans-Kristian Arntzen 2024-11-06 17:31:37 +01:00 • committed by Marge Bot
parent 437bd63265
commit 5f70858ece
1 changed files with 65 additions and 33 deletions
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98
src/vulkan/wsi/wsi_common_wayland.c
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@ -1149,41 +1149,47 @@ wsi_wl_surface_get_support(VkIcdSurfaceBase *surface,
return VK_SUCCESS;
}
/* For true mailbox mode, we need at least 4 images:
* 1) One to scan out from
* 2) One to have queued for scan-out
* 3) One to be currently held by the Wayland compositor
* 4) One to render to
*/
#define WSI_WL_BUMPED_NUM_IMAGES 4
/* Catch-all. 3 images is a sound default for everything except MAILBOX. */
#define WSI_WL_DEFAULT_NUM_IMAGES 3
static uint32_t
wsi_wl_surface_get_min_image_count(struct wsi_wl_display *display,
const VkSurfacePresentModeEXT *present_mode)
{
/* With legacy frame callback mechanism, report 4 images by default, unless
* EXT_surface_maintenance1 query is used to ask explicitly for FIFO. */
if (present_mode && (present_mode->presentMode == VK_PRESENT_MODE_FIFO_KHR ||
present_mode->presentMode == VK_PRESENT_MODE_FIFO_RELAXED_KHR)) {
if (display->fifo_manager) {
/* When FIFO protocol is supported, applications will no longer block
* in QueuePresentKHR due to frame callback, so returning 4 images
* for a FIFO swapchain is problematic due to excessive latency. This
* latency can only be limited through means of presentWait which few
* applications use.
* 2 images are enough for forward progress, but 3 is used here
* because 2 could result in waiting for the compositor to remove an
* old image from scanout when we'd like to be rendering.
*/
return 3;
}
/* If we receive a FIFO present mode, only 2 images is required for forward progress.
* Performance with 2 images will be questionable, but we only allow it for applications
* using the new API, so we don't risk breaking any existing apps this way.
* Other ICDs expose 2 images here already. */
return 2;
} else {
/* For true mailbox mode, we need at least 4 images:
* 1) One to scan out from
* 2) One to have queued for scan-out
* 3) One to be currently held by the Wayland compositor
* 4) One to render to
*/
return 4;
if (present_mode) {
return present_mode->presentMode == VK_PRESENT_MODE_MAILBOX_KHR ?
WSI_WL_BUMPED_NUM_IMAGES : WSI_WL_DEFAULT_NUM_IMAGES;
}
/* If explicit present_mode is not being queried, we need to provide a safe "catch-all"
* which can work for any presentation mode. Implementations are allowed to bump the minImageCount
* on swapchain creation, so this limit should be the lowest value which can guarantee forward progress. */
/* When FIFO protocol is not supported, we always returned 4 here,
* despite it going against the spirit of minImageCount in the specification.
* To avoid any unforeseen breakage, just keep using the same values we always have.
* In this path, we also never consider bumping the image count in minImageCount in swapchain creation time. */
/* When FIFO protocol is supported, applications will no longer block
* in QueuePresentKHR due to frame callback, so returning 4 images
* for a FIFO swapchain is deeply problematic due to excessive latency.
* This latency can only be limited through means of presentWait which few applications use, and we cannot
* mandate that shipping applications are rewritten to avoid a regression.
* 2 images are enough for forward progress in FIFO, but 3 is used here as a pragmatic decision
* because 2 could result in waiting for the compositor to remove an
* old image from scanout when we'd like to be rendering,
* and we don't want naively written applications to head into poor performance territory by default.
* X11 backend has very similar logic and rationale here.
*/
return display->fifo_manager ? WSI_WL_DEFAULT_NUM_IMAGES : WSI_WL_BUMPED_NUM_IMAGES;
}
static VkResult
@ -2760,9 +2766,10 @@ wsi_wl_surface_create_swapchain(VkIcdSurfaceBase *icd_surface,
old_chain->retired = true;
}
int num_images = pCreateInfo->minImageCount;
size_t size = sizeof(*chain) + num_images * sizeof(chain->images[0]);
/* We need to allocate the chain handle early, since display initialization code relies on it.
* We do not know the actual image count until we have initialized the display handle,
* so allocate conservatively in case we need to bump the image count. */
size_t size = sizeof(*chain) + MAX2(WSI_WL_BUMPED_NUM_IMAGES, pCreateInfo->minImageCount) * sizeof(chain->images[0]);
chain = vk_zalloc(pAllocator, size, 8, VK_SYSTEM_ALLOCATION_SCOPE_OBJECT);
if (chain == NULL)
return VK_ERROR_OUT_OF_HOST_MEMORY;
@ -2802,6 +2809,31 @@ wsi_wl_surface_create_swapchain(VkIcdSurfaceBase *icd_surface,
if (result != VK_SUCCESS)
goto fail;
uint32_t num_images = pCreateInfo->minImageCount;
/* If app provides a present mode list from EXT_swapchain_maintenance1,
* we don't know which present mode will be used.
* Application is assumed to be well-behaved and be spec-compliant.
* It needs to query all per-present mode minImageCounts individually and use the max() of those modes,
* so there should never be any need to bump image counts. */
bool uses_present_mode_group = vk_find_struct_const(
pCreateInfo->pNext, SWAPCHAIN_PRESENT_MODES_CREATE_INFO_EXT) != NULL;
/* If FIFO manager is not used, minImageCount is already the bumped value for reasons outlined in
* wsi_wl_surface_get_min_image_count(), so skip any attempt to bump the counts. */
if (wsi_wl_surface->display->fifo_manager && !uses_present_mode_group) {
/* With proper FIFO, we return a lower minImageCount to make FIFO viable without requiring the use of KHR_present_wait.
* The image count for MAILBOX should be bumped for performance reasons in this case.
* This matches strategy for X11. */
const VkSurfacePresentModeEXT mode =
{ VK_STRUCTURE_TYPE_SURFACE_PRESENT_MODE_EXT, NULL, pCreateInfo->presentMode };
uint32_t min_images = wsi_wl_surface_get_min_image_count(wsi_wl_surface->display, &mode);
bool requires_image_count_bump = min_images == WSI_WL_BUMPED_NUM_IMAGES;
if (requires_image_count_bump)
num_images = MAX2(min_images, num_images);
}
VkPresentModeKHR present_mode = wsi_swapchain_get_present_mode(wsi_device, pCreateInfo);
if (present_mode == VK_PRESENT_MODE_IMMEDIATE_KHR) {
chain->tearing_control =