Merge pull request #11416 from lifupan/prealloc

runtime-rs: add the memory prealloc support for qemu/ch

src/runtime-rs/config/configuration-cloud-hypervisor.toml.in

@@ -177,6 +177,15 @@ block_device_driver = "virtio-blk-pci"
 # Default false
 #block_device_cache_direct = true
 
+# Enable pre allocation of VM RAM, default false
+# Enabling this will result in lower container density
+# as all of the memory will be allocated and locked
+# This is useful when you want to reserve all the memory
+# upfront or in the cases where you want memory latencies
+# to be very predictable
+# Default false
+#enable_mem_prealloc = true
+
 # Enable huge pages for VM RAM, default false
 # Enabling this will result in the VM memory
 # being allocated using huge pages.

src/runtime-rs/crates/hypervisor/ch-config/src/convert.rs

@@ -285,6 +285,8 @@ impl TryFrom<(MemoryInfo, GuestProtection)> for MemoryConfig {
 
             hotplug_size,
 
+            prefault: mem.enable_mem_prealloc,
+
             ..Default::default()
         };
 

src/runtime-rs/crates/hypervisor/src/qemu/cmdline_generator.rs

@@ -625,6 +625,7 @@ struct MemoryBackendFile {
     size: u64,
     share: bool,
     readonly: bool,
+    prealloc: bool,
 }
 
 impl MemoryBackendFile {
@@ -635,6 +636,7 @@ impl MemoryBackendFile {
             size,
             share: false,
             readonly: false,
+            prealloc: false,
         }
     }
 
@@ -647,6 +649,11 @@ impl MemoryBackendFile {
         self.readonly = readonly;
         self
     }
+
+    fn set_prealloc(&mut self, prealloc: bool) -> &mut Self {
+        self.prealloc = prealloc;
+        self
+    }
 }
 
 #[async_trait]
@@ -658,6 +665,10 @@ impl ToQemuParams for MemoryBackendFile {
         params.push(format!("mem-path={}", self.mem_path));
         params.push(format!("size={}", format_memory(self.size)));
         params.push(format!("share={}", if self.share { "on" } else { "off" }));
+        params.push(format!(
+            "prealloc={}",
+            if self.prealloc { "on" } else { "off" }
+        ));
         params.push(format!(
             "readonly={}",
             if self.readonly { "on" } else { "off" }
@@ -2261,6 +2272,10 @@ impl<'a> QemuCmdLine<'a> {
             MemoryBackendFile::new("entire-guest-memory-share", "/dev/shm", self.memory.size);
         mem_file.set_share(true);
 
+        if self.config.memory_info.enable_mem_prealloc {
+            mem_file.set_prealloc(true);
+        }
+
         // don't put the /dev/shm memory backend file into the anonymous container,
         // there has to be at most one of those so keep it by name in Memory instead
         //self.devices.push(Box::new(mem_file));