1. Response time
Refers to the time from the client's request to the entire process of getting a response. In some tools, the request response time is usually referred to as "TTLB" (Time to last byte), which means the time from when a request is initiated to the time the client receives the last byte of the response.
Calculation model of response time:
Response time = network transmission time (request) + server processing time (one layer or multiple layers) + network transmission time (response) + page parsing time
Simplified calculation model of browser response time:
Browser response time = server response time + page loading time + page rendering time
The page rendering time mainly consists of two parts:
Page rendering time = script execution time + browser engine rendering time
2. Guiding ideas:
"2-5-10 principle", simply put, when the user can get a response within 2 seconds, they will feel that the system responds quickly;
When the user gets a response within 2 seconds, the system will feel that the response is very fast;
When users get a response within 2-5 seconds, they will feel that the response speed of the system is OK;
When the user gets a response within 5-10 seconds, the system will feel that the response speed of the system is very slow, but it is acceptable;
When the user still cannot get a response after more than 8 seconds, he will feel that the system is terrible, or think that the system has lost the response, and choose to leave the Web site or initiate a second request.
2 seconds ~ home page, 5 seconds ~ normal page, 10 seconds ~ complex query page.
In performance testing, the "reasonable response time" depends on the user's needs and cannot be determined by the tester's own assumptions.
(Additional References) End User Response Time:
It refers to the time from when the user triggers a page request to when the page is fully displayed, sometimes referred to as the browser response time.
End-user response time is the end-user's intuitive perception of an application's performance. It consists of three parts:
Page request and download time (referred to as page download time).
Server response time.
Browser processing and rendering time.
Expressed in a formula, that is:
End user response time = page download time + server response time + browser processing and rendering time
The relationship between network latency, number of HTTP requests, concurrency, and total latency consumed is:
Total latency = network latency × number of HTTP requests / degree of concurrency
And the simplified model of page download time is:
页面下载时间 = 在带宽上消耗的时间 + 在网络延迟上消耗的时间 = 页面尺寸 / 网络带宽 + （网络延迟 × HTTP 请求数）/ 并发度
在这个简化模型中，有些因子没有被考虑 :
DNS 查询时间；
HTTP 请求建立时间；
HTTP 连接的连接保持状态；
浏览器，服务器在处理传输时消耗的时间，等等；
带宽对并发度的影响。
基于这个模型，我们只要测量出页面的尺寸、HTTP 请求数和并发度就可以推测在不同网络条件下的页面下载时间。