The document discusses optimizing KVM virtual machines for performance by focusing on compute resources like CPU and memory, storage, and networking. It provides recommendations for hardware configuration including processors, RAM, and network interfaces, as well as software optimizations in the host OS, hypervisor, guest OS, and device drivers. Finally, it lists some good references for further information on virtual machine performance tuning.

1. Optimizing KVM virtual
machines
for performance
Boyan Krosnov
Chief of Product
StorPool Storage

2. ● Better application performance -- e.g. time to load a page, time to rebuild,
time to execute specific query
● Happier customers (in cloud / multi-tenant environments)
● Lower cost per delivered resource (per VM)
○ through higher density
Why optimize

3. ● Compute - CPU and memory
● Storage
● Network
● Do you optimize for throughput or for latency?
Where:
● VM, guest OS, drivers, etc.
● Host OS and hypervisor
● Host hardware
● Network
● Storage system
What

4. Typically 2x 10GE per hypervisor for storage traffic
Same or separate 2x 10GE for internet and inter-VM traffic
Typical cluster has just 2 switches. Up to 96x 10GE ports at low cost.
We are starting to see 40/56 GigE clusters and we expect many 25 GigE networks
in the next year.
VLANs, Jumbo frames, flow control.
RDMA
A word on networks

5. Typically
- 2x E5-2697v3 -- 28 cores, 56 threads, @3.1GHz all-cores turbo
- 256-384-512 GB RAM
- 10/40 GigE NICs with RDMA
-
- firmware versions and BIOS settings matter
- Understand power management -- esp. C-states and P-states
- Think of rack level optimization - how do we get the lowest total cost per
delivered resource.
A word on host hardware

6. RHEL7 Virtualization_Tuning_and_Optimization_Guide
Also
https://pve.proxmox.com/wiki/Performance_Tweaks
http://events.linuxfoundation.org/sites/events/files/slides/CloudOpen2013_Khoa_Huynh_v3.pdf
http://www.linux-kvm.org/images/f/f9/2012-forum-virtio-blk-performance-improvement.pdf
http://www.slideshare.net/janghoonsim/kvm-performance-optimization-for-ubuntu
… but don’t trust everything you read. Perform your own benchmarking!
Good references

7. Recent Linux kernel, KVM and QEMU
… but beware of the bleeding edge
E.g. qemu-kvm-ev from RHEV (repackaged by CentOS)
tuned-adm virtual-host
tuned-adm virtual-guest
Host OS, guest OS

8. ● Use virtio-net driver
● regular virtio vs vhost_net
● SR-IOV (PCIe pass-through)
Networking

9. ● cache=none -- direct IO, bypass host buffer cache
● io=native -- use Linux Native AIO, not POSIX AIO (threads)
●
● virtio-blk -> dataplane
● virtio-scsi -> multiqueue
●
● in guest virtio_blk.queue_depth 128 -> 256
Block I/O

10. - balloon
- KSM (RAM dedup)
- huge pages, THP
- NUMA
- use local-node memory if you can
- route IRQs of network and storage adapters to a core on the node they are on
Compute - Memory

11. Pinning
HT
NUMA
Compute - CPU

12. Demo

13. Boyan Krosnov
b k @ storool.com
@bkrosnov
https://storpool.com/