Link button inside the gridview calling modalpopup extender slowness issue

Hi,

In the below code i have faced problem if iam calling modalpopexteder through linkbutton it is taking more time can anybody please help how i can fix slowness on linkbutton click posting data (Sent data is around 2.10MB to server to open popup)may be this is causing issue please suggest me.

<asp:Content ID="Content1" ContentPlaceHolderID="MNMBody" runat="server"><asp:UpdatePanel ID="updatepanel1" runat="server"><ContentTemplate><asp:Panel ID="pnl1" runat="server" Style="width: 99.5%; margin-left: 2px;"><asp:Panel ID="pnlgvDetails" runat="server" Style="-ms-overflow: auto; overflow: auto;
                                width: 1000px; border: none;" ScrollBars="Vertical" Height="370px"><asp:GridView ID="gvDetails" runat="server" AutoGenerateColumns="False" AllowSorting="False"
                                    PageSize="10" AllowPaging="False" CssClass="gvStyle paddingbottom100px" BorderWidth="0px"
                                    CellPadding="2" CellSpacing="1" OnRowDataBound="gvDetails_RowDataBound" OnRowCommand="gvDetails_RowCommand"
                                    ShowHeader="true" OnPageIndexChanging="gvDetailsPageIndexChanging" Style="width: 4000px;"
                                    EmptyDataText="You have no results to display. Please Add items from Cart."><HeaderStyle ForeColor="#333333" CssClass="gvHeaderStyle backgroundcolore1e0d7"></HeaderStyle><PagerStyle CssClass="DatagridPagerstyle textalignleft" HorizontalAlign="Left" /><RowStyle CssClass="gvItemStyle" /><Columns><asp:TemplateField HeaderText="Line Notes"><ItemTemplate><asp:LinkButton ID="lbtnLineNotes" Text="Line Notes" runat="server"
                                                            CommandArgument='<%# Eval("OrderItemID") %>' CommandName="NotesInfo" ></asp:LinkButton></ItemTemplate><ItemStyle CssClass="textaligncenter" Width="85px" /><HeaderStyle HorizontalAlign="Center"></HeaderStyle></asp:TemplateField></Columns></asp:GridView></asp:Panel></asp:Panel></ContentTemplate><Triggers><asp:PostBackTrigger ControlID="btnManageViews" /></Triggers></asp:UpdatePanel><asp:ModalPopupExtender runat="server" BackgroundCssClass="ModalPopupBG" ID="ModalPopupOrderLineItemNotes"
        PopupControlID="pnlOrderLineItemNotes" TargetControlID="lnkModelPopupControlTarget"
        X="280"></asp:ModalPopupExtender><asp:LinkButton ID="lnkModelPopupControlTarget" runat="server" Style="display: none;"></asp:LinkButton><asp:Panel Style="display: none; width: 65%; height: 250px;" ID="pnlOrderLineItemNotes"
        runat="server" ClientIDMode="Static"><asp:UpdatePanel runat="server" ID="UpdatePanel3"><ContentTemplate><asp:GridView ID="gvHeaderNotes" Width="100%" AutoGenerateColumns="False" runat="server"
                                ShowHeaderWhenEmpty="true" ClientIDMode="Static" AutoGenerateSelectButton="false"
                                OnSelectedIndexChanged="gvHeaderNotes_SelectedIndexChanged" OnRowCommand="gvHeaderNotes_OnRowCommand"
                                CellPadding="3" CellSpacing="1" BorderWidth="0px" GridLines="None"><PagerSettings FirstPageImageUrl="~/ui/images/PaginateFirst.gif" LastPageImageUrl="~/ui/images/PaginateLast.gif"
                                    Mode="NumericFirstLast" NextPageImageUrl="~/ui/images/PaginateNext.gif" PreviousPageImageUrl="~/ui/images/PaginatePrevious.gif"
                                    FirstPageText="First page" LastPageText="Last page" /><HeaderStyle CssClass="gvHeadLink" ForeColor="#333333" /><RowStyle HorizontalAlign="Center" CssClass="gvItemStyle" /><EmptyDataTemplate><asp:Label ID="lblRow" runat="server" Text="You have no results to display"></asp:Label></EmptyDataTemplate><Columns></Columns><PagerStyle HorizontalAlign="Left" VerticalAlign="Middle" CssClass="gvPagerStyle"
                                    Width="20%" /><AlternatingRowStyle CssClass="gvAlternatingItem" /><SelectedRowStyle CssClass="gvRowOn" Font-Bold="false" /></asp:GridView></ContentTemplate><Triggers><asp:AsyncPostBackTrigger ControlID="ddlcodedesc" EventName="SelectedIndexChanged" /><asp:AsyncPostBackTrigger ControlID="ddlPreNotes" EventName="SelectedIndexChanged" /></Triggers></asp:UpdatePanel></asp:Panel><asp:UpdateProgress ID="UpdateProgress5" runat="server" DisplayAfter="100" DynamicLayout="true"
        AssociatedUpdatePanelID="UpdatePanel3"><ProgressTemplate><div class="Progressbar"><div style="text-align: center; padding-top: 2%;">
                    Please wait...</div><div style="text-align: center; padding-top: 3%;"><img src="../../../UI/images/ProgressStatus.gif" alt="Please wait..." /></div></div></ProgressTemplate></asp:UpdateProgress></asp:Content>