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hypervisor, vmm: Remove shared ownership of VmmOps

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This interface is used by the vCPU thread to delegate responsibility for
handling MMIO/PIO operations and to support different approaches than a
VM exit.

During profiling I found that we were spending 13.75% of the boot CPU
uage acquiring access to the object holding the VmmOps via
ArcSwap::load_full()

    13.75%     6.02%  vcpu0            cloud-hypervisor    [.] arc_swap::ArcSwapAny<T,S>::load_full
            |
            ---arc_swap::ArcSwapAny<T,S>::load_full
               |
                --13.43%--<hypervisor::kvm::KvmVcpu as hypervisor::cpu::Vcpu>::run
                          std::sys_common::backtrace::__rust_begin_short_backtrace
                          core::ops::function::FnOnce::call_once{{vtable-shim}}
                          std::sys::unix::thread::Thread::new::thread_start

However since the object implementing VmmOps does not need to be mutable
and it is only used from the vCPU side we can change the ownership to
being a simple Arc<> that is passed in when calling create_vcpu().

This completely removes the above CPU usage from subsequent profiles.

Signed-off-by: Rob Bradford <robert.bradford@intel.com>
This commit is contained in:
Rob Bradford
2020-11-18 16:37:52 +00:00
committed by Samuel Ortiz
parent 6a591ca81d
commit 0fec326582
5 changed files with 46 additions and 48 deletions
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4
hypervisor/src/vm.rs
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@@ -174,7 +174,7 @@ pub trait Vm: Send + Sync {
/// Unregister an event that will, when signaled, trigger the `gsi` IRQ.
fn unregister_irqfd(&self, fd: &EventFd, gsi: u32) -> Result<()>;
/// Creates a new KVM vCPU file descriptor and maps the memory corresponding
fn create_vcpu(&self, id: u8) -> Result<Arc<dyn Vcpu>>;
fn create_vcpu(&self, id: u8, vmmops: Option<Arc<Box<dyn VmmOps>>>) -> Result<Arc<dyn Vcpu>>;
/// Registers an event to be signaled whenever a certain address is written to.
fn register_ioevent(
&self,
@@ -220,8 +220,6 @@ pub trait Vm: Send + Sync {
fn state(&self) -> Result<VmState>;
/// Set the VM state
fn set_state(&self, state: VmState) -> Result<()>;
/// Set VmmOps interface
fn set_vmmops(&self, vmmops: Box<dyn VmmOps>) -> Result<()>;
/// Get dirty pages bitmap
fn get_dirty_log(&self, slot: u32, memory_size: u64) -> Result<Vec<u64>>;
}