I have a problem with sqlservr.exe (version 2008). It use a more memory. I checked on windows taskbar manager, sqlservr.exe usage ( Mem usage - 8GB Ram). I dont know how can I fix it.Got the following metrics of the server using Perfmon:

SQLServer:Buffer Manager
Buffer cache hit ratio
13 SQLServer:Buffer Manager
Page lookups/sec
46026128096 SQLServer:Buffer Manager
Free pages
129295 SQLServer:Buffer Manager
Total pages
997309 SQLServer:Buffer Manager
Target pages
1053560 SQLServer:Buffer Manager
Database pages
484117 SQLServer:Buffer Manager
Reserved pages
0 SQLServer:Buffer Manager
Stolen pages
383897 SQLServer:Buffer Manager
Lazy writes/sec
384369 SQLServer:Buffer Manager
Readahead pages/sec
69315446 SQLServer:Buffer Manager
Page reads/sec
71280353 SQLServer:Buffer Manager
Page writes/sec
12408371 SQLServer:Buffer Manager
Checkpoint pages/sec
7053801 SQLServer:Buffer Manager
Page life expectancy
735262 SQLServer:General Statistics
Active Temp Tables
161 SQLServer:General Statistics
Temp Tables Creation Rate
3131845 SQLServer:General Statistics
Logins/sec
2336011 SQLServer:General Statistics
Logouts/sec
2335984 SQLServer:General Statistics
User Connections
27 SQLServer:General Statistics
Transactions
0 SQLServer:Access Methods
Full Scans/sec
34422821 SQLServer:Access Methods
Range Scans/sec
2027247756 SQLServer:Access Methods
Workfiles Created/sec
49771600 SQLServer:Access Methods
Worktables Created/sec
28205828 SQLServer:Access Methods
Index Searches/sec
4890715219 SQLServer:Access Methods
FreeSpace Scans/sec
21178928 SQLServer:Access Methods
FreeSpace Page Fetches/sec
21226653 SQLServer:Access Methods
Pages Allocated/sec
41483279 SQLServer:Access Methods
Extents Allocated/sec
4743504 SQLServer:Access Methods
Extent Deallocations/sec
4806606 SQLServer:Access Methods
Page Deallocations/sec
41419137 SQLServer:Access Methods
Page Splits/sec
23834799 SQLServer:Memory Manager
SQL Cache Memory (KB)
29160 SQLServer:Memory Manager
Target Server Memory (KB)
8428480 SQLServer:Memory Manager
Total Server Memory (KB)
7978472

Some body could help me please.And I really want to know the cause for the above.