# Unable to max out CPU in KVM environment
**URL:** https://discuss.aerospike.com/t/unable-to-max-out-cpu-in-kvm-environment/1798
**Category:** Aerospike Server Benchmarks
**Tags:** benchmark
**Created:** [September 9, 2015, 6:52pm UTC](https://discuss.aerospike.com/t/unable-to-max-out-cpu-in-kvm-environment/1798 "2015-09-09T18:52:10Z")
**Posts on this page:** 2
**Page:** 1
### Author:  [@jin\_dev](https://discuss.aerospike.com/u/jin_dev)
#### Post date: [September 9, 2015, 6:52pm UTC](https://discuss.aerospike.com/t/unable-to-max-out-cpu-in-kvm-environment/1798/1 "2015-09-09T18:52:10Z")
I am currently doing performance benchmarking of Aerospike database in VM environment.
Following is the setup-\>
- Storage-engine - In-memory
- Cluster size - 2 Node Heartbeat type -
- Multicast (tried Mesh as well)
-
# of network interfaces - 2 \* 1 Gbps (1 for client-server and another for cluster)
- Other config details - service-threads and transaction-queues parameter matches # of vCPUs available.
- Client - Aerospike benchmark utility. Tried with varying number of threads starting from 20 up to 700. Data size - String of length 100 and 500. (Tried up to 3 clients with 4 vCPUs each)
- Operation - 100 % Write
I am running performing tests on Openstack public cloud. Following is our observation →
**No of vCPUs / TPS / Server Side CPU utilization (%)**
* * *
- 2 / 22-23k / 180
- 4 / 28-29k / 245
- 8 / 60-62k / 520
Neither the client vCPU nor the network were the bottleneck.
Also tried the similar setup in my local lab, where results were similar. In my local setup, I even tried with separating out CPU for network I/O and Aerospike using the smp\_affinity setting and taskset, there was no change in the observation.
Questions -
1. Apart from “service-threads” and “transaction-queues” is there any other config parameter that needs to be tweaked?
2. What could be the other reasons for not able to max out the CPU for higher number of vCPUs ?
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### Author:  [@sunil](https://discuss.aerospike.com/u/sunil)
#### Post date: [September 11, 2015, 10:02am UTC](https://discuss.aerospike.com/t/unable-to-max-out-cpu-in-kvm-environment/1798/2 "2015-09-11T10:02:57Z")
In general, there are more factor’s that may effect VM environments, but I am surprised that you are observing the same behavior in local (non-VM) setup too.
When doing our benchmarks in non-VM environment, on a 8 CPU machine, we are able to use the CPU upto 700%. One important question here is…“What all you are accounting ?”. Do you also consider the system time ? Or the numbers quoted by you are (100-idle%) ? If you can share the output of top command from both the VM and non-VM environments, it will help.
3 4vCPU clients may not be able to saturate 2-node 8CPU server node. You can try to increase the clients and see if you can push more throughput. You can see that in a 2vCPU server nodes, the cpu util % is high. It drops as the cores on the server are increasing. It could be because of thread context switching too.
Can you try 100% read load too ? I see that you are doing 100% write load. Aerospike does sync replication over the network. May be the replication component is not catching up. We will know this if you do 100% read load. I am expecting to see higher CPU utilization in this workload.