How eclipse closes XML file validation

I don't know what happened today. The STS (Eclipse) validates the XML file very slowly, as follows:

Workaround: (Go from http://blog.csdn.net/aigochina/article/details/8196486)

Turn off XML validation

1. Menu "Windows"-"preperences"-"Validation"
2. Find "XML Validator" on the right, and leave the "Bulid" checkbox unchecked, keeping "Manual" selected, as we finally need to ensure the correctness of the XML, which can be selected by selecting the XML file and selecting "Validate" in the right-click menu. Manual to verify, if the XML is wrong, will pop-up window prompt, but if the "Manual" check box is also canceled, and then manually verify, even if the XML is really wrong, it will not be correctly prompted.

How eclipse closes XML file validation