virtmgr: Pass hugepages to crosvm
Now crosvm applies block alignment ("arm64: Align RAM region with the
block size") when mmaping the RAM region for a VM, it is possible to
back this memory with THP (transparent-hugepages). This is controlled by
either the VM config option "hugepages" or the "bin/vm" option
"--hugepages"
Enabling --hugepages makes crosvm "madvise(MADV_HUGEPAGE)" that region.
This will have at the moment no effect on Android as the default value
for /sys/kernel/mm/transparent_hugepages/shmem_enabled is [never].
However, it'll enable OEMs to turn on the feature by tweaking the latter
knob.
Using THP brings a significant performance improvement by reducing the
number of fault necessary when using a VM (/512 for a 4K pages Arm
machine) and reducing the pressure on the TLB (for both stage-1 and
stage-2). However, finding huge pages might be a difficult task when the
system has been running for a long time and the memory is quite
fragmented. khugepaged helps promoting pages to huge-pages but running
it has a cost and might delay the memory allocation depending on the
chosen defrag policy.
Bug: 278011447
Change-Id: I954f93df4f08ad015958d36d115d9f9e0c3547b5
diff --git a/virtualizationmanager/src/crosvm.rs b/virtualizationmanager/src/crosvm.rs
index 040e552..b426051 100644
--- a/virtualizationmanager/src/crosvm.rs
+++ b/virtualizationmanager/src/crosvm.rs
@@ -121,6 +121,7 @@
pub device_tree_overlay: Option<File>,
pub display_config: Option<DisplayConfig>,
pub input_device_options: Vec<InputDeviceOption>,
+ pub hugepages: bool,
}
#[derive(Debug)]
@@ -1005,6 +1006,11 @@
});
}
}
+
+ if config.hugepages {
+ command.arg("--hugepages");
+ }
+
append_platform_devices(&mut command, &mut preserved_fds, &config)?;
debug!("Preserving FDs {:?}", preserved_fds);