From 42d62d423ae602d57f85c0b9daddecdd00b4eb1f Mon Sep 17 00:00:00 2001
From: cosmonaut <evan@moonside.games>
Date: Fri, 1 Mar 2024 15:38:18 -0800
Subject: [PATCH] limit max frames in flight

---
 src/Refresh_Driver_Vulkan.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/src/Refresh_Driver_Vulkan.c b/src/Refresh_Driver_Vulkan.c
index c899c80..cc4d589 100644
--- a/src/Refresh_Driver_Vulkan.c
+++ b/src/Refresh_Driver_Vulkan.c
@@ -80,6 +80,7 @@ typedef struct VulkanExtensions
 #define UBO_BUFFER_SIZE 16777216 				/* 16MB */
 #define MAX_UBO_SECTION_SIZE 4096 			        /* 4KB */
 #define DESCRIPTOR_POOL_STARTING_SIZE 128
+#define MAX_FRAMES_IN_FLIGHT 3
 #define WINDOW_DATA "Refresh_VulkanWindowData"
 
 #define IDENTITY_SWIZZLE 		\
@@ -875,6 +876,8 @@ typedef struct VulkanSwapchainData
 	/* Synchronization primitives */
 	VkSemaphore imageAvailableSemaphore;
 	VkSemaphore renderFinishedSemaphore;
+
+	uint32_t submissionsInFlight;
 } VulkanSwapchainData;
 
 typedef struct WindowData
@@ -4639,6 +4642,7 @@ static uint8_t VULKAN_INTERNAL_CreateSwapchain(
 	uint32_t i;
 
 	swapchainData = SDL_malloc(sizeof(VulkanSwapchainData));
+	swapchainData->submissionsInFlight = 0;
 
 	/* Each swapchain must have its own surface. */
 
@@ -9616,6 +9620,12 @@ static Refresh_Texture* VULKAN_AcquireSwapchainTexture(
 
 	swapchainData = windowData->swapchainData;
 
+	/* Drop frames if too many submissions in flight */
+	if (swapchainData->submissionsInFlight >= MAX_FRAMES_IN_FLIGHT)
+	{
+		return NULL;
+	}
+
 	/* Window is claimed but swapchain is invalid! */
 	if (swapchainData == NULL)
 	{
@@ -10057,6 +10067,11 @@ static void VULKAN_INTERNAL_CleanCommandBuffer(
 
 	/* Reset presentation data */
 
+	for (i = 0; i < commandBuffer->presentDataCount; i += 1)
+	{
+		commandBuffer->presentDatas[i].windowData->swapchainData->submissionsInFlight -= 1;
+	}
+
 	commandBuffer->presentDataCount = 0;
 	commandBuffer->waitSemaphoreCount = 0;
 	commandBuffer->signalSemaphoreCount = 0;
@@ -10255,6 +10270,10 @@ static void VULKAN_Submit(
 				presentData->windowData
 			);
 		}
+		else
+		{
+			presentData->windowData->swapchainData->submissionsInFlight += 1;
+		}
 	}
 
 	/* Check if we can perform any cleanups */