GC
- free your object as soon as possible (this will help to prevent the object promotion to into higher GC generation)
- long lived object create early (this will help to avoid memory defragmentation by setting long lived (promoted to 1 and 2) object at bottom of CLR memory block)
- avoid implementing finalizes in your class (so the object does not survive collection process)
- avoid referencing a short lived objects from a long lived object ()
- assign your reference to null (nothing) as soon as possible, especially before making a call to a long method
- identify objects with a long lifespan and use CLR Profiler to analyze the reasons
- avoid complicated object nesting and hierarchy (it make object graphing complex and expensive, as the GC walks all roots and builds a graph of reachable objects.)
- use .NET Memory Performance Counters to identify possible problems in GC
- use Performance Counter to monitor .NET counters:
- if “% Time in GC” >50% it is too much
- ideal ratio for these counters should be “# Gen 0 Collections” : “# Gen 1 Collections” : “# Gen 2 Collections” = 100: 10 : 1
JIT optimization (skipped if used NGEN)
- do not set to null(nothing) all local variables (it is set to null by JIT to optimize GC)
- enregistration – frequently called local variables stored in CPU registry instead of stack
- pitching – if the system low on memory the native code is removed from memory
- inlining – for methods smaller than 8-10 lines (<32b compiled) with no loops it is placed in caller body
Exception handling approach
- use only when need try-catch block (it is expensive)
- apply error handlers from top to bottom
- do not use exceptions to control the program flow or for business exceptions only for exceptional situations
- do not derive custom exception from Application Exception (adds unnecessary depth)
- add automated exception logging inside the custom exceptions
- exceptions is a class – use property for new message – do not parse
- when rethrow use Throw nor Throw ThisException (so original exceptions context is saved) although it is a good practice to let CLR to propagate the exception
- exceptions should be attributed with for remote calls or WS
- use validations to avoid exceptions
- avoid exceptions in loops
Performance settings and coding
- set Remove Integer Overflow Check (project settings-compile) (checks overflow if for loop) saves 20% in integer-long operations
- set Option Strict On (project settings-compile) to avoid implicit unboxing
- avoid SPLIT function
- use DirectCast not CType for references (for unboxing values, for casting variable of base class to variable of derived class)
- use StringBuilder for string concatenations
