There is already support of enabling dirty log gradually in small chunks
for x86 in commit 3c9bd4006b ("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
c862626e19