Some formulas for system performance and concurrency

Some formulas for system performance and concurrency

Concurrency per unit time

QPS(TPS)=Number of concurrency/average response time
QPS(TPS): Number of requests/transactions per second
Number of concurrency: Number of requests/transactions processed by the system at the same time
Response time: AverageTake the average response time

Maximum number of threads

Max number of threads=(MaxProcessMemory – JVMMemory – ReservedOsMemory) / (ThreadStackSize)

Number of threads that can be started per unit time

Number of startup threads=(task execution time/(task execution time-IO waiting time))*CPU cores

Number of simultaneous online households

With or without thinking time (T_think), the TPS value obtained from the test and the number of concurrent virtual users (U_concurrent) and the transaction response time (T_response) read by Loadrunner have the following relationship (in stable operation):
TPS=U_concurrent / (T_response+T_think).

Response time: the time it takes to respond to a request

Network transmission time: N1+N2+N3+N4
Application server processing time: A1+A3
Database server processing time: A2
Response time=N1+N2+N3+N4+A1+A3+A2

The formula for calculating the number of concurrent users

Number of system users: The rated number of users of the system, such as an OA system, the total number of users who may use the system is 5000, then this number is the number of system users.
Number of simultaneous online users: the maximum number of simultaneous online users within a certain time range.
The number of simultaneous online users = the number of requests per second RPS (throughput) + the number of concurrent connections + the average user thinking time
The calculation of the average number of concurrent users: C=nL / T
where C is the average concurrentThe number of users, n is the average number of users accessing the system per day (login session), L is the average time from login to logout within a day (the average time of the login session), T is the length of the investigation time (how long does a user use the system in a day))
Calculation of the peak number of concurrent users: C^ is approximately equal to C + 3*root number C
where C^ is the peak number of concurrent users, C is the average number of concurrent users, the formula follows the Poisson distribution theory.

Calculation formula for throughput:

F: Throughput, VU: Number of virtual users, R: Number of requests issued by each virtual user, T: Time spent in performance testing
F=VU * R / T

Performance Counters

Resource utilization = actual resource usage/total resource availability

Calculation formula for thinking time

T: Time
TS: User think time
R = T / TS

General steps for calculating think time:

A. First calculate the number of concurrent users in the system
C=nL / T F=R×C
B. Calculate the average throughput of the system
F=VU * R / T R×C =VU * R / T
C, count the average number of requests sent by each user
R=u*C*T/VU
D, calculate the thinking time according to the formula
TS=T/R

Reference address:
https://blog.csdn.net/workdsz/article/details/78417108 Performance test performance indicators
https://www.zhihu.com/question/21556347 PV, TPS, How is QPS calculated
https://en.wikipedia.org/wiki/TPS_report Encyclopedia knowledge