Overview
============
This series of patches is to optimize the performance of
online migration using dirty ring and autoconverge.
Mainly through the following aspects to do optimization:
1. When using the dirty ring mode to traverse each memslot
to obtain dirty pages, only call log_sync_global once,
because log_sync_global collects the dirty pages of all
memslots on all CPUs.
2. Dynamically adjust the dirty ring collection thread to
reduce the occurrence of ring full, thereby reducing the
impact on customers, improving the efficiency of dirty
page collection, and thus improving the migration efficiency.
3. When collecting dirty pages from KVM,
kvm_cpu_synchronize_kick_all is not called if the rate is
limited, and it is called only once before suspending the
virtual machine. Because kvm_cpu_synchronize_kick_all will
become very time-consuming when the CPU is limited, and
there will not be too many dirty pages, so it only needs
to be called once before suspending the virtual machine to
ensure that dirty pages will not be lost and the efficiency
of migration is guaranteed .
4. Based on the characteristic of collecting dirty pages
in the dirty ring, a new dirty page rate calculation method
is proposed to obtain a more accurate dirty page rate.
5. Use a more accurate dirty page rate and calculate the
matching speed limit threshold required to complete the
migration according to the current system bandwidth and
parameters, instead of the current speed limit by constantly
trying this time-consuming method, reducing the need for
practical Meaningful trial process, greatly reducing
migration time.
Testing
=======
Test environment:
Host: 64 cpus(Intel(R) Xeon(R) Gold 5218 CPU @ 2.30GHz),
512G memory,
10G NIC
VM: 2 cpus,4G memory and 8 cpus, 32G memory
memory stress: run stress(qemu) in VM to generates memory stress
Test1: Massive online migration(Run each test item 50 to 200 times)
Test command: virsh -t migrate $vm --live --p2p --unsafe
--undefinesource --persistent --auto-converge --migrateuri
tcp://${data_ip_remote}
*********** Use optimized dirtry ring ***********
ring_size mem_stress VM average_migration_time(ms)
4096 1G 2C4G 15888
4096 3G 2C4G 13320
65536 1G 2C4G 10036
65536 3G 2C4G 12132
4096 4G 8C32G 53629
4096 8G 8C32G 62474
4096 30G 8C32G 99025
65536 4G 8C32G 45563
65536 8G 8C32G 61114
65536 30G 8C32G 102087
*********** Use Unoptimized dirtry ring ***********
ring_size mem_stress VM average_migration_time(ms)
4096 1G 2C4G 23992
4096 3G 2C4G 44234
65536 1G 2C4G 24546
65536 3G 2C4G 44939
4096 4G 8C32G 88441
4096 8G 8C32G may not complete
4096 30G 8C32G 602884
65536 4G 8C32G 335535
65536 8G 8C32G 1249232
65536 30G 8C32G 616939
*********** Use bitmap dirty tracking ***********
ring_size mem_stress VM average_migration_time(ms)
0 1G 2C4G 24597
0 3G 2C4G 45254
0 4G 8C32G 103773
0 8G 8C32G 129626
0 30G 8C32G 588212
Test1 result:
Compared with the old bitmap method and the unoptimized dirty ring,
the migration time of the optimized dirty ring from the sorted data
is greatly improved, especially when the virtual machine memory is
large and the memory pressure is high, the effect is more obvious,
can achieve five to six times the migration acceleration effect.
And during the test, it was found that the dirty ring could not be
completed for a long time after adding certain memory pressure.
The optimized dirty ring did not encounter such a problem.
Test2: qemu guestperf test
Test ommand parameters: --auto-converge --stress-mem XX --downtime 300
--bandwidth 10000
*********** Use optimized dirtry ring ***********
ring_size stress VM Significant_perf max_memory_update cost_time(s)
_drop_duration(s) speed(ms/GB)
4096 3G 2C4G 5.5 2962 23.5
65536 3G 2C4G 6 3160 25
4096 3G 8C32G 13 7921 38
4096 6G 8C32G 16 11.6K 46
4096 10G 8C32G 12.1 11.2K 47.6
4096 20G 8C32G 20 20.2K 71
4096 30G 8C32G 29.5 29K 94.5
65536 3G 8C32G 14 8700 40
65536 6G 8C32G 15 12K 46
65536 10G 8C32G 11.5 11.1k 47.5
65536 20G 8C32G 21 20.9K 72
65536 30G 8C32G 29.5 29.1K 94.5
*********** Use Unoptimized dirtry ring ***********
ring_size stress VM Significant_perf max_memory_update cost_time(s)
_drop_duration(s) speed(ms/GB)
4096 3G 2C4G 23 2766 46
65536 3G 2C4G 22.2 3283 46
4096 3G 8C32G 62 48.8K 106
4096 6G 8C32G 68 23.87K 124
4096 10G 8C32G 91 16.87K 190
4096 20G 8C32G 152.8 28.65K 336.8
4096 30G 8C32G 187 41.19K 502
65536 3G 8C32G 71 12.7K 67
65536 6G 8C32G 63 12K 46
65536 10G 8C32G 88 25.3k 120
65536 20G 8C32G 157.3 25K 391
65536 30G 8C32G 171 30.8K 487
*********** Use bitmap dirty tracking ***********
ring_size stress VM Significant_perf max_memory_update cost_time(s)
_drop_duration(s) speed(ms/GB)
0 3G 2C4G 18 3300 38
0 3G 8C32G 38 7571 66
0 6G 8C32G 61.5 10.5K 115.5
0 10G 8C32G 110 13.68k 180
0 20G 8C32G 161.6 24.4K 280
0 30G 8C32G 221.5 28.4K 337.5
Test2 result:
The above test data shows that the guestperf performance of the
optimized dirty ring during the migration process is significantly
better than that of the unoptimized dirty ring, and slightly better
than the bitmap method.
During the migration process of the optimized dirty ring, the migration
time is greatly reduced, and the time in the period of significant
memory performance degradation is significantly shorter than that of
the bitmap mode and the unoptimized dirty ring mode. Therefore, the
optimized ditry ring can better reduce the impact on guests accessing
memory resources during the migration process.
Please review, thanks.
Chongyun Wu (5):
kvm,memory: Optimize dirty page collection for dirty ring
kvm: Dynamically control the load of the reaper thread
kvm: Dirty ring autoconverge optmization for kvm_cpu_synchronize_kick_all
kvm: Introduce a dirty rate calculation method based on dirty ring
migration: Calculate the appropriate throttle for autoconverge
accel/kvm/kvm-all.c | 239 ++++++++++++++++++++++++++++++++++++--
include/sysemu/cpus.h | 1 +
include/sysemu/kvm.h | 2 +
migration/migration.c | 13 ++++++
migration/migration.h | 2 +
migration/ram.c | 64 +++++++++++++++++++++++--
softmmu/cpus.c | 18 ++++++++
softmmu/memory.c | 6 +++
8 files changed, 316 insertions(+), 29 deletions(-)
--
1.8.3.1
--
Best Regard,
Chongyun Wu
