Creating a debugfs directory for each virtual machine is a suprisingly costly operation as one has to synchronize multiple cores. However, short living VMs seldom benefit from it. Since there are valid use-cases we make this feature optional via a module parameter. Disabling it saves 150us in the hello microbenchmark. Signed-off-by: Bernhard Kauer <bk@xxxxxxxxx> --- virt/kvm/kvm_main.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a48861363649..760e39cf86a8 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -94,6 +94,9 @@ unsigned int halt_poll_ns_shrink = 2; module_param(halt_poll_ns_shrink, uint, 0644); EXPORT_SYMBOL_GPL(halt_poll_ns_shrink); +bool debugfs_per_vm = true; +module_param(debugfs_per_vm, bool, 0644); + /* * Ordering of locks: * @@ -1050,7 +1053,7 @@ static int kvm_create_vm_debugfs(struct kvm *kvm, const char *fdname) int kvm_debugfs_num_entries = kvm_vm_stats_header.num_desc + kvm_vcpu_stats_header.num_desc; - if (!debugfs_initialized()) + if (!debugfs_initialized() || !debugfs_per_vm) return 0; snprintf(dir_name, sizeof(dir_name), "%d-%s", task_pid_nr(current), fdname); -- 2.45.2
