From c862626e19efdc26b26481515470b160e8fe52f3 Mon Sep 17 00:00:00 2001 From: Keqian Zhu Date: Mon, 13 Apr 2020 20:20:23 +0800 Subject: KVM: arm64: Support enabling dirty log gradually in small chunks There is already support of enabling dirty log gradually in small chunks for x86 in commit 3c9bd4006bfc ("KVM: x86: enable dirty log gradually in small chunks"). This adds support for arm64. x86 still writes protect all huge pages when DIRTY_LOG_INITIALLY_ALL_SET is enabled. However, for arm64, both huge pages and normal pages can be write protected gradually by userspace. Under the Huawei Kunpeng 920 2.6GHz platform, I did some tests on 128G Linux VMs with different page size. The memory pressure is 127G in each case. The time taken of memory_global_dirty_log_start in QEMU is listed below: Page Size Before After Optimization 4K 650ms 1.8ms 2M 4ms 1.8ms 1G 2ms 1.8ms Besides the time reduction, the biggest improvement is that we will minimize the performance side effect (because of dissolving huge pages and marking memslots dirty) on guest after enabling dirty log. Signed-off-by: Keqian Zhu Signed-off-by: Marc Zyngier Link: https://lore.kernel.org/r/20200413122023.52583-1-zhukeqian1@huawei.com --- Documentation/virt/kvm/api.rst | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'Documentation/virt') diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index efbbe570aa9b..0017f63fa44f 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -5777,7 +5777,7 @@ will be initialized to 1 when created. This also improves performance because dirty logging can be enabled gradually in small chunks on the first call to KVM_CLEAR_DIRTY_LOG. KVM_DIRTY_LOG_INITIALLY_SET depends on KVM_DIRTY_LOG_MANUAL_PROTECT_ENABLE (it is also only available on -x86 for now). +x86 and arm64 for now). KVM_CAP_MANUAL_DIRTY_LOG_PROTECT2 was previously available under the name KVM_CAP_MANUAL_DIRTY_LOG_PROTECT, but the implementation had bugs that make -- cgit v1.2.3