prepare for windows impl

src/linux/gpu/nvidia.rs

@@ -0,0 +1,56 @@
+use crate::data::{GpuMemory, GpuUsage};
+use nvml_wrapper::enum_wrappers::device::TemperatureSensor;
+use nvml_wrapper::{Device, Nvml};
+use once_cell::sync::Lazy;
+
+static NVIDIA: Lazy<Option<Nvml>> = Lazy::new(|| Nvml::init().ok());
+
+fn device() -> Option<Device<'static>> {
+    NVIDIA.as_ref()?.device_by_index(0).ok()
+}
+
+pub fn temperature() -> Option<f32> {
+    let temp = device()?.temperature(TemperatureSensor::Gpu).ok()?;
+    Some(temp as f32)
+}
+
+pub fn power() -> Option<u64> {
+    device()?
+        .total_energy_consumption()
+        .ok()
+        .map(|mj| mj * 1_000)
+}
+
+pub fn memory() -> Option<GpuMemory> {
+    let mem = device()?.memory_info().ok()?;
+    Some(GpuMemory {
+        total: mem.total,
+        free: mem.free,
+    })
+}
+
+pub fn utilization() -> impl Iterator<Item = GpuUsage> {
+    let sources = if let Some(device) = device() {
+        let utilization = device.utilization_rates().ok();
+        [
+            ("compute", utilization.as_ref().map(|u| u.gpu)),
+            ("memory", utilization.as_ref().map(|u| u.gpu)),
+            (
+                "encode",
+                device.encoder_utilization().ok().map(|u| u.utilization),
+            ),
+            (
+                "decode",
+                device.decoder_utilization().ok().map(|u| u.utilization),
+            ),
+        ]
+    } else {
+        [("", None); 4]
+    };
+    sources.into_iter().flat_map(|(system, usage)| {
+        Some(GpuUsage {
+            system,
+            usage: usage?,
+        })
+    })
+}