[performance test] 3 How to calculate the number of concurrent users

What is concurrency

Look at the picture above , If we arrive at the system strictly according to logic , The absolute number of concurrent users is 4; But if it is used to describe 1s Number of concurrent users in , It is 16

however , In fact, the allocation of users should be as follows

So you should only describe concurrency , There is no need for absolute or relative , So it is recommended to use TPS To host the concept of concurrency , Concurrency is 16PTS, Namely 1s The internal system handles 16 One transaction .

Number of online users / How to calculate the number of concurrent users

Pictured above , All in all 32 Systems entered the system , But the green user doesn't do anything , So the number of online users is 32, The number of concurrent users is 16, The concurrency is 50%

however , The system is usually as follows ,

According to this cached service , The number of online users depends on the capacity of the cache service , The maximum number of users on the way plus timeout .

Here's the picture , Explain the relationship between the number of online users and the number of concurrent users and the concurrent threads of the press

1. If there is 10000 Number of online users , The concurrency is 1, Then the number of concurrent users is 100
2. If each thread's TPS yes 20, The average response time is 50ms, Then the press only needs to be started 5 Threads ok 了
3. about server Come on , What it deals with is 100TPS, The average response time is 50ms, The calculation for the 1000ms/20TPS
4. If server There are also two threads on the end , So a thread TPS It is 50
5. among , Conversion from the number of concurrent users to the number of concurrent threads of the press , It's actually the first step in benchmarking

Sum up ：TPS The calculation formula of is

TPS = 1000ms/(RT)* Number of press threads