3.1.1 (7s) vs 3.5.1 (15s) on 200×25K Cells

[dimka124]

I have a table with 200 columns and 25,000 rows. Most cells contain string data (including Dates/Numbers), which I set up like this:

Looping by rows, then by columns:

csharp
var cell = new DocumentFormat.OpenXml.Spreadsheet.Cell { CellReference = ... };
...
cell.DataType = CellValues.String;
cell.CellValue = new CellValue(s);
cell.InlineString = null;
...
I write the cells using openXmlWriter.WriteElement(cell).

Performance issue:

v3.1.1: File creates in 7 seconds
v3.5.1: File creates in 15 seconds (more than 2x slower)

Question: How can I speed up v3.5.1 to match or beat v3.1.1 performance?

[dimka124]

3.5.1 15 sec
3.2.0-3.4.1 14 sec
3.1.1 7 sec