
%         Registration           Examining Linux 2.6 Page-Cache Performance   
%  [2]Register/Submit Proposal Sonny Rao (raosanth@us.ibm.com)                


Given the current trends towards ubiquitous    
64-bit server/desktop computing with large     
amounts of cheap system memory, the            
performance and structure of the Linux         
page-cache will undoubtedly become more        
important in the future, and we believe an     
analytical and empirical examination of        
performance will be valuable in guiding future 
development.                                   

The current 2.6 radix-tree based design        
represents a huge leap forward from the old    
global hash-table design, but we also beleive  
there may be some issues with the current      
radix-tree structure itself.                   

We have three main concerns about the current  
implementation:                                

\begin{enumerate}
\item Radix tree keys are unnecessarily long      
especially on LP64 systems which can cause     
radix trees to perform poorly                  

\item The common case of in-order insertion of    
pages into the radix tree could most-likely be 
improved                                       

\item Parallel access to the radix-tree structure 
\end{enumerate}

We will cover our analysis of the current      
implementation and discuss potential           
improvements for these issues using a          
combination of analytical models and our       
measurements of improvement using              
proof-of-concept implementations of ideas such 
as: extendible hashing techniques, trading     
space for time by altering the \ident{MAP_SHIFT}
setup, using smaller radix keys combined with  
larger logical page sizes, and possibly        
others.                                        


