We tried to set the pageSize before reloading ( "dataBind" ) the grid.
From the debugging we did, it was noticed that right after setting the new dataSource (even though the dataSource itself has the new value of the pageSize ) the last value is applied again so what we see in the UI is flicker.
For a second or so the new ( "25" ) size is set and right after that the grid goes to the previous old value.


                                var jsonPDataSourceOptions = {
                                    urlType: 'remoteUrl',
                                    dataSource: ajaxUrl,
                                    paging: {
                                        enabled: true,
                                        pageSize: 25
                                    },
                                    responseDataKey: 'd.results.data'
                                };

                                var igDs = new $.ig.JSONPDataSource(jsonPDataSourceOptions);
                                igDs.pageSize(25);
                                self.options.gridOptions.dataSource = igDs;
                                
                                
                                $(self.options.jobsGridSelector, self.element).igGrid("option", "dataSource", igDs);
                                $(self.options.jobsGridSelector, self.element).igGrid("dataBind");