From 4689e98fe884d9412b72fd6293b6d6a69e3ef68e Mon Sep 17 00:00:00 2001 From: Bas Nieuwenhuizen Date: Sun, 28 Apr 2019 01:50:36 +0200 Subject: [PATCH] vulkan/wsi: Set X11 minImageCount to 3. For IMMEDIATE and FIFO, most games work in a pipelined manner where the can produce frames at a rate of 1/MAX(CPU duration, GPU duration), but the render latency is CPU duration + GPU duration. This means that with scanout from pageflipping we need 3 frames to run full speed: 1) CPU rendering work 2) GPU rendering work 3) scanout Once we have a nonblocking acquire that returns a semaphore we can merge 1 and 3. Hence the ideal implementation needs only 2 images, but games cannot tellwe currently do not have an ideal implementation and that hence they need to allocate 3 images. So let us do it for them. This is a tradeoff as it uses more memory than needed for non-fullscreen and non-performance intensive applications. Since this is pretty much a TODO that can use the context I added this as a comment. Acked-by: Jason Ekstrand Acked-by: Samuel Pitoiset --- src/vulkan/wsi/wsi_common_x11.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-) diff --git a/src/vulkan/wsi/wsi_common_x11.c b/src/vulkan/wsi/wsi_common_x11.c index 46f1c08b453..96aba03aca2 100644 --- a/src/vulkan/wsi/wsi_common_x11.c +++ b/src/vulkan/wsi/wsi_common_x11.c @@ -501,13 +501,25 @@ x11_surface_get_capabilities(VkIcdSurfaceBase *icd_surface, VK_COMPOSITE_ALPHA_OPAQUE_BIT_KHR; } - /* 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 X server - * 4) One to render to + /* For IMMEDIATE and FIFO, most games work in a pipelined manner where the + * can produce frames at a rate of 1/MAX(CPU duration, GPU duration), but + * the render latency is CPU duration + GPU duration. + * + * This means that with scanout from pageflipping we need 3 frames to run + * full speed: + * 1) CPU rendering work + * 2) GPU rendering work + * 3) scanout + * + * Once we have a nonblocking acquire that returns a semaphore we can merge + * 1 and 3. Hence the ideal implementation needs only 2 images, but games + * cannot tellwe currently do not have an ideal implementation and that + * hence they need to allocate 3 images. So let us do it for them. + * + * This is a tradeoff as it uses more memory than needed for non-fullscreen + * and non-performance intensive applications. */ - caps->minImageCount = 2; + caps->minImageCount = 3; /* There is no real maximum */ caps->maxImageCount = 0;