Save web.xml eclipse time will go by xsd verify its declaration, and its xsd is downloaded from the network, and save a lot of xsd this address, eclipse will be downloaded, it is particularly slow.
The above process can be observed by wireshark capture.
So delete xsi: schemaLocation after nodes, the speed will be faster very much.
This approach is undermining the xsi: schemaLocation syntax, there will be a prompt, but does not affect use. But eventually it should be restored.