xml serialization - How would I solve this .net web server performance profiling issue? -

i using redgate performance profiler test asp.net mvc 2 application. 1 of things found out xmlserializer taking of cpu time referring this post. changed uses xmlserializercache now.

now xmlserializer issue no longer there , profiling application simulating 80 users @ same time using website jmeter. top methods take time doing firstordefault() on data pulling give example-

var values=(from c in datacontext.table1            join s in datacontext.table2 on new { c.id, c.date }              equals new { s.id, s.date } list                           c.id== id && c.date == date                           s in list.defaultifempty()                           select new daydto()                           {                               points = c.points,                               points1 = c.points1,                               points2 = c.points2,                               points3 = c.points3,                               points4 = c.points4                           }).firstordefault(); 

can suggest me can improve ? current times 25 secs , 16 secs top 2 methods .. because simulating 80 user @ same time , there issues on database (sql server 2005) side table being large , indexing etc...and trying identify issues see code i.e. issues on c# side..

i appreciate !

this assumes top time "inclusive time", not "exclusive time".

inclusive time means includes code called method, in case firstordefault execute database call. database calls expensive in context of latency, cpu thread blocked , not using cpu while waiting database call.

first should ask if problem, not affect throughput (assuming database server can handle load), latency of calls.

if problem need speed actual sql query. should start sql profiler, catch actual question, run in sql management studio. @ execution plan see if query slower expected , try figure out why. if slow might check indexing start with.