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. Signed-off-by: Bernhard Kauer <bk@xxxxxxxxx> --- v1->v2: read-write parameter to avoid killing all running VMs to toggle it v2->v3: invert the logic, add documentation Documentation/admin-guide/kernel-parameters.txt | 4 ++++ virt/kvm/kvm_main.c | 5 ++++- 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index d401577b5a6a..8ae3dc4f2392 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2723,6 +2723,10 @@ If the value is 0 (the default), KVM will pick a period based on the ratio, such that a page is zapped after 1 hour on average. + kvm.uevent_notify= + [KVM] Send a uevent message to udev whenever a VM is + created or destroyed. Default is true. + kvm-amd.nested= [KVM,AMD] Control nested virtualization feature in KVM/SVM. Default is 1 (enabled). diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 609e0bd68e8e..276c98e2c37d 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); +static bool uevent_notify = true; +module_param(uevent_notify, bool, 0644); + /* * Ordering of locks: * @@ -6276,7 +6279,7 @@ 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 || !uevent_notify) return; mutex_lock(&kvm_lock); -- 2.45.2
