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authorKeqian Zhu <zhukeqian1@huawei.com>2020-04-13 20:20:23 +0800
committerMarc Zyngier <maz@kernel.org>2020-05-16 15:05:02 +0100
commitc862626e19efdc26b26481515470b160e8fe52f3 (patch)
treee9ef5a63c372c89f85404e6b58fc5683455fd9c8 /Documentation/virt
parent0529c9021252a58b6d3808da86986a614b900b1b (diff)
downloadlinux-c862626e19efdc26b26481515470b160e8fe52f3.tar.bz2
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 <zhukeqian1@huawei.com> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20200413122023.52583-1-zhukeqian1@huawei.com
Diffstat (limited to 'Documentation/virt')
-rw-r--r--Documentation/virt/kvm/api.rst2
1 files changed, 1 insertions, 1 deletions
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