vkd3d: Implement frame rate limiter.

Follows the same logic as DXVK. Instead of delaying presentation, we instead delay
signaling of the frame latency event for hopefully consistent frame pacing on the
app side.

DXGI will call SetTargetFrameRate with a negative value when running in fullscreen
mode with a fixed refresh rate and Vsync enabled. The intent is to only engage the
frame rate limiter if the actual display refresh rate does not match the display
mode that the app is running at.

Signed-off-by: Philip Rebohle <philip.rebohle@tu-dortmund.de>

libs/vkd3d/swapchain.c

@@ -78,6 +78,23 @@ struct present_wait_entry
     uint64_t begin_frame_time_ns;
 };
 
+#if defined(_WIN32)
+typedef UINT (WINAPI *PFN_NtDelayExecution) (BOOL, LARGE_INTEGER*);
+typedef UINT (WINAPI *PFN_NtQueryTimerResolution) (ULONG*, ULONG*, ULONG*);
+typedef UINT (WINAPI *PFN_NtSetTimerResolution) (ULONG, BOOL, ULONG*);
+#endif
+
+struct platform_sleep_state
+{
+#if defined(_WIN32)
+    PFN_NtDelayExecution NtDelayExecution;
+    PFN_NtQueryTimerResolution NtQueryTimerResolution;
+    PFN_NtSetTimerResolution NtSetTimerResolution;
+#endif
+
+    uint64_t sleep_threshold_ns;
+};
+
 struct dxgi_vk_swap_chain
 {
     IDXGIVkSwapChain2 IDXGIVkSwapChain_iface;
@@ -195,6 +212,20 @@ struct dxgi_vk_swap_chain
         uint64_t time;
     } frame_statistics;
 
+    struct
+    {
+        pthread_mutex_t lock;
+
+        bool enable;
+        bool has_user_override;
+        uint64_t target_interval_ns;
+        uint64_t next_deadline_ns;
+        uint64_t frame_timestamps[16];
+        uint32_t frame_window_index;
+
+        struct platform_sleep_state sleep_state;
+    } frame_rate_limit;
+
     struct
     {
         VkSurfaceFormatKHR *formats;
@@ -386,6 +417,8 @@ static void dxgi_vk_swap_chain_cleanup(struct dxgi_vk_swap_chain *chain)
     pthread_cond_destroy(&chain->wait_thread.cond);
     vkd3d_free(chain->wait_thread.wait_queue);
 
+    pthread_mutex_destroy(&chain->frame_rate_limit.lock);
+
     vkd3d_native_sync_handle_destroy(chain->frame_latency_event);
     vkd3d_native_sync_handle_destroy(chain->frame_latency_event_internal);
 
@@ -1178,7 +1211,40 @@ static void STDMETHODCALLTYPE dxgi_vk_swap_chain_GetFrameStatistics(IDXGIVkSwapC
 
 static void STDMETHODCALLTYPE dxgi_vk_swap_chain_SetTargetFrameRate(IDXGIVkSwapChain2 *iface, double frame_rate)
 {
-    FIXME("iface %p, frame_rate %lf stub!\n", iface, frame_rate);
+    struct dxgi_vk_swap_chain *chain = impl_from_IDXGIVkSwapChain(iface);
+
+    TRACE("iface %p, frame_rate %lf.\n", iface, frame_rate);
+
+    /* Env var takes priority over the display mode and config option */
+    if (chain->frame_rate_limit.has_user_override)
+        return;
+
+    pthread_mutex_lock(&chain->frame_rate_limit.lock);
+
+    if (frame_rate != 0.0)
+    {
+        /* Target frame rate may be negative, in which case we should only engage the limiter
+         * if the measured frame rate is higher than expected, e.g. due to the actual display
+         * refresh rate not matching the display mode used for the swap chain. */
+        INFO("Set target frame rate to %.1lf FPS.\n", fabs(frame_rate));
+
+        chain->frame_rate_limit.enable = frame_rate > 0.0;
+        chain->frame_rate_limit.target_interval_ns = (uint64_t)(1.0e9 / fabs(frame_rate));
+        chain->frame_rate_limit.next_deadline_ns = 0;
+
+        memset(chain->frame_rate_limit.frame_timestamps, 0, sizeof(chain->frame_rate_limit.frame_timestamps));
+        chain->frame_rate_limit.frame_window_index = 0;
+    }
+    else
+    {
+        if (chain->frame_rate_limit.enable)
+            INFO("Disabling frame rate limit.\n");
+
+        chain->frame_rate_limit.enable = false;
+        chain->frame_rate_limit.target_interval_ns = 0;
+    }
+
+    pthread_mutex_unlock(&chain->frame_rate_limit.lock);
 }
 
 static CONST_VTBL struct IDXGIVkSwapChain2Vtbl dxgi_vk_swap_chain_vtbl =
@@ -2429,6 +2495,8 @@ static void dxgi_vk_swap_chain_signal_waitable_handle(struct dxgi_vk_swap_chain
     dxgi_vk_swap_chain_push_present_id(chain, present_count, present_id, chain->request.begin_frame_time_ns);
 }
 
+static void dxgi_vk_swap_chain_delay_next_frame(struct dxgi_vk_swap_chain *chain, uint64_t current_time_ns);
+
 static void dxgi_vk_swap_chain_present_callback(void *chain_)
 {
     const struct dxgi_vk_swap_chain_present_request *next_request;
@@ -2496,6 +2564,8 @@ static void dxgi_vk_swap_chain_present_callback(void *chain_)
     if (!chain->wait_thread.supports_present_wait)
     {
         dxgi_vk_swap_chain_try_acquire_next_image(chain);
+        dxgi_vk_swap_chain_delay_next_frame(chain, vkd3d_get_current_time_ns());
+
         /* The old implementation used acquire semaphores, and did not block, so to maintain same behavior,
          * defer blocking on the VkFence. */
         if (vkd3d_native_sync_handle_is_valid(chain->present_request_done_event))
@@ -2526,6 +2596,117 @@ static void dxgi_vk_swap_chain_update_frame_statistics(struct dxgi_vk_swap_chain
     spinlock_release(&chain->frame_statistics.lock);
 }
 
+static void dxgi_vk_swap_chain_platform_sleep_for_ns(struct platform_sleep_state *sleep_state, uint64_t duration_ns)
+{
+#if defined(_WIN32)
+    LARGE_INTEGER ticks;
+
+    if (sleep_state->NtDelayExecution)
+    {
+        /* Ticks are in units of 100ns, with negative values indicating a
+         * duration and positive values an absolute time in tick counts. */
+        ticks.QuadPart = (int64_t)duration_ns / -100;
+
+        /* Set alertable = false to avoid wineserver round-trips */
+        sleep_state->NtDelayExecution(FALSE, &ticks);
+    }
+    else
+    {
+        Sleep(duration_ns / 1000000);
+    }
+#else
+    struct timespec duration;
+
+    (void)sleep_state;
+
+    duration.tv_sec = duration_ns / 1000000000;
+    duration.tv_nsec = duration_ns % 1000000000;
+
+    /* ignore interrupts */
+    nanosleep(&duration, NULL);
+#endif
+}
+
+static void dxgi_vk_swap_chain_delay_next_frame(struct dxgi_vk_swap_chain *chain, uint64_t current_time_ns)
+{
+    struct platform_sleep_state *sleep_state = &chain->frame_rate_limit.sleep_state;
+    uint64_t window_start_time_ns, window_total_time_ns;
+    uint64_t sleep_threshold_ns, sleep_duration_ns;
+    uint64_t next_deadline_ns = 0;
+
+    pthread_mutex_lock(&chain->frame_rate_limit.lock);
+
+    if (chain->frame_rate_limit.target_interval_ns)
+    {
+        if (!chain->frame_rate_limit.enable)
+        {
+            const uint32_t window_size = ARRAY_SIZE(chain->frame_rate_limit.frame_timestamps);
+
+            window_start_time_ns = chain->frame_rate_limit.frame_timestamps[chain->frame_rate_limit.frame_window_index % window_size];
+
+            chain->frame_rate_limit.frame_timestamps[chain->frame_rate_limit.frame_window_index % window_size] = current_time_ns;
+            chain->frame_rate_limit.frame_window_index += 1;
+
+            window_total_time_ns = current_time_ns - window_start_time_ns;
+
+            /* Enable the frame rate limiter if frames are being delivered faster than expected.
+             * Discard the first window of data since it may be inaccurate, especially if we do
+             * not hit the present_wait path. Allow for a 3% error. */
+            if (chain->frame_rate_limit.frame_window_index >= 2 * window_size)
+            {
+                chain->frame_rate_limit.enable = 103 * window_total_time_ns < 100 * window_size * chain->frame_rate_limit.target_interval_ns;
+
+                if (chain->frame_rate_limit.enable)
+                {
+                    INFO("Measured frame rate of %.1lf FPS exceeds desired refresh rate of %.1lf Hz, enabling limiter.\n",
+                            1.0e9 / (double)(window_total_time_ns) * (double)(window_size),
+                            1.0e9 / (double)(chain->frame_rate_limit.target_interval_ns));
+                }
+            }
+        }
+
+        if (chain->frame_rate_limit.enable)
+        {
+            next_deadline_ns = chain->frame_rate_limit.next_deadline_ns;
+
+            /* Each frame is assigned a time window [t0,t1) during which presentation is expected to
+             * complete, with its duration being equal to one frame interval. If a frame completes
+             * before t1, just advance the next frame's time window by one frame interval and sleep
+             * as necessary, otherwise reset the sequence using the current time as a starting point,
+             * which should roughly line up with a display refresh. */
+            if (current_time_ns < next_deadline_ns + chain->frame_rate_limit.target_interval_ns)
+                chain->frame_rate_limit.next_deadline_ns += chain->frame_rate_limit.target_interval_ns;
+            else
+                chain->frame_rate_limit.next_deadline_ns = current_time_ns + chain->frame_rate_limit.target_interval_ns;
+        }
+    }
+
+    pthread_mutex_unlock(&chain->frame_rate_limit.lock);
+
+    if (current_time_ns >= next_deadline_ns)
+        return;
+
+    /* Busy-wait for the last couple of milliseconds for accuracy, only use the
+     * platform's sleep function for durations longer than the threshold, which
+     * is an estimated error based on the timer interval and sleep duration. */
+    sleep_duration_ns = next_deadline_ns - current_time_ns;
+    sleep_threshold_ns = sleep_state->sleep_threshold_ns + sleep_duration_ns / 6;
+
+    while (sleep_duration_ns > sleep_threshold_ns)
+    {
+        dxgi_vk_swap_chain_platform_sleep_for_ns(sleep_state, sleep_duration_ns - sleep_threshold_ns);
+
+        current_time_ns = vkd3d_get_current_time_ns();
+        sleep_duration_ns = next_deadline_ns > current_time_ns ? next_deadline_ns - current_time_ns : 0;
+    }
+
+    while (current_time_ns < next_deadline_ns)
+    {
+        vkd3d_pause();
+        current_time_ns = vkd3d_get_current_time_ns();
+    }
+}
+
 static void *dxgi_vk_swap_chain_wait_worker(void *chain_)
 {
     struct dxgi_vk_swap_chain *chain = chain_;
@@ -2562,15 +2743,17 @@ static void *dxgi_vk_swap_chain_wait_worker(void *chain_)
                         entry.id, UINT64_MAX));
             }
             vkd3d_queue_timeline_trace_complete_present_wait(timeline_trace, cookie);
-
-            if (entry.begin_frame_time_ns)
-                end_frame_time_ns = vkd3d_get_current_time_ns();
         }
         else
         {
             dxgi_vk_swap_chain_drain_complete_semaphore(chain, entry.present_count);
         }
 
+        end_frame_time_ns = vkd3d_get_current_time_ns();
+
+        if (chain->wait_thread.supports_present_wait)
+            dxgi_vk_swap_chain_delay_next_frame(chain, end_frame_time_ns);
+
         dxgi_vk_swap_chain_update_frame_statistics(chain, entry.present_count);
 
         if (vkd3d_native_sync_handle_is_valid(chain->frame_latency_event))
@@ -2714,6 +2897,76 @@ static HRESULT dxgi_vk_swap_chain_init_low_latency(struct dxgi_vk_swap_chain *ch
     return S_OK;
 }
 
+static HRESULT dxgi_vk_swap_chain_init_sleep_state(struct platform_sleep_state *sleep_state)
+{
+#if defined(_WIN32)
+    uint64_t sleep_granularity_ns;
+    ULONG min, max, cur;
+    HMODULE ntdll;
+    bool is_wine;
+
+    is_wine = !!GetModuleHandleW(L"winevulkan.dll");
+
+    if ((ntdll = GetModuleHandleW(L"ntdll.dll")))
+    {
+        sleep_state->NtQueryTimerResolution = (void*)GetProcAddress(ntdll, "NtQueryTimerResolution");
+        sleep_state->NtSetTimerResolution = (void*)GetProcAddress(ntdll, "NtSetTimerResolution");
+        sleep_state->NtDelayExecution = (void*)GetProcAddress(ntdll, "NtDelayExecution");
+    }
+
+    /* Older versions of Wine do not implement these functions, be robust here. */
+    if (sleep_state->NtQueryTimerResolution && !sleep_state->NtQueryTimerResolution(&min, &max, &cur))
+    {
+        sleep_granularity_ns = 100 * cur;
+
+        if (sleep_state->NtSetTimerResolution && !sleep_state->NtSetTimerResolution(max, TRUE, &cur))
+            sleep_granularity_ns = 100 * max;
+
+        INFO("Timer interval is %.1lf ms.\n", (double)sleep_granularity_ns / 1.0e6);
+    }
+    else
+    {
+        sleep_granularity_ns = 1000000;  /* 1ms */
+    }
+
+    /* This should always be available, however we can fall back to plain old Sleep() if not. */
+    if (!sleep_state->NtDelayExecution)
+        FIXME("NtDelayExecution not found in ntdll.\n");
+
+    sleep_state->sleep_threshold_ns = (is_wine ? 1 : 4) * sleep_granularity_ns;
+    return S_OK;
+#else
+    /* On native builds, we use nanosleep. Assume reasonable accuracy down to 1ms. */
+    sleep_state->sleep_threshold_ns = 1000000;
+    return S_OK;
+#endif
+}
+
+static HRESULT dxgi_vk_swap_chain_init_frame_rate_limiter(struct dxgi_vk_swap_chain *chain)
+{
+    double target_frame_rate;
+    char env[16];
+
+    pthread_mutex_init(&chain->frame_rate_limit.lock, NULL);
+
+    if (vkd3d_get_env_var("VKD3D_FRAME_RATE", env, sizeof(env)) ||
+            vkd3d_get_env_var("DXVK_FRAME_RATE", env, sizeof(env)))
+    {
+        target_frame_rate = strtod(env, NULL);
+
+        if (target_frame_rate > 0.0)
+        {
+            INFO("Set frame rate limit to %.1lf FPS via environment.\n", target_frame_rate);
+
+            chain->frame_rate_limit.enable = true;
+            chain->frame_rate_limit.has_user_override = true;
+            chain->frame_rate_limit.target_interval_ns = (uint64_t)(1.0e9 / target_frame_rate);
+        }
+    }
+
+    return dxgi_vk_swap_chain_init_sleep_state(&chain->frame_rate_limit.sleep_state);
+}
+
 static HRESULT dxgi_vk_swap_chain_init(struct dxgi_vk_swap_chain *chain, IDXGIVkSurfaceFactory *pFactory,
         const DXGI_SWAP_CHAIN_DESC1 *pDesc, struct d3d12_command_queue *queue)
 {
@@ -2746,6 +2999,9 @@ static HRESULT dxgi_vk_swap_chain_init(struct dxgi_vk_swap_chain *chain, IDXGIVk
     if (FAILED(hr = dxgi_vk_swap_chain_init_low_latency(chain)))
         goto err;
 
+    if (FAILED(hr = dxgi_vk_swap_chain_init_frame_rate_limiter(chain)))
+        goto err;
+
     ID3D12CommandQueue_AddRef(&queue->ID3D12CommandQueue_iface);
     return S_OK;