server load.. please help..

my server has high load, below is top output :

Code: 
top - 01:56:00 up 5 days, 23:24,  1 user,  load average: 1.74, 1.61, 1.58
Tasks: 292 total,   1 running, 290 sleeping,   1 stopped,   0 zombie
Cpu(s): 49.5% us,  4.6% sy,  0.0% ni, 42.3% id,  2.3% wa,  1.3% hi,  0.0% si
Mem:   2067644k total,  1385972k used,   681672k free,     8064k buffers
Swap:  4192956k total,    11384k used,  4181572k free,   440772k cached
what's caused this high load? Cpu is 42% idle and swap memory is not used much.

TiA

 

 

 

 

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