Handling of uevents in userlevel is a bottleneck for tiny VMs. Running 10_000 VMs keeps one and a half cores busy for 5.4 seconds to let systemd-udevd handle all messages. That is roughly 27x longer than the 0.2 seconds needed for running the VMs without them. We choose a module parameter here due to its simplicity and ease of maintenance. v1->v2: make the parameter read-write to avoid reboots on ARM 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 38620c16739b..9e714cf45617 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -97,6 +97,9 @@ EXPORT_SYMBOL_GPL(halt_poll_ns_shrink); bool debugfs_per_vm = true; module_param(debugfs_per_vm, bool, 0644); +bool disable_uevent_notify; +module_param(disable_uevent_notify, bool, 0644); + /* * Allow direct access (from KVM or the CPU) without MMU notifier protection * to unpinned pages. @@ -6141,7 +6144,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm) struct kobj_uevent_env *env; unsigned long long created, active; - if (!kvm_dev.this_device || !kvm) + if (!kvm_dev.this_device || !kvm || disable_uevent_notify) return; mutex_lock(&kvm_lock); -- 2.45.2
