postgres 9.0.4 configuration and performance issue

The top command gave us the following

            pci, instance #5
    pci, instance #5
load averages:  17.5,  18.1,  18.6;                    up 673+23:00:23                                                                                                   16:33:58
156 processes: 140 sleeping, 16 on cpu
CPU states: 76.5% idle, 22.8% user,  0.7% kernel,  0.0% iowait,  0.0% swap
Memory: 64G phys mem, 19G free mem, 63G total swap, 63G free swap

   PID USERNAME LWP PRI NICE  SIZE   RES STATE    TIME    CPU COMMAND
  7041 postgres   1   0    0 3180M 3174M cpu/26 113:08  1.59% postgres
 22787 postgres   1   0    0 3181M 3174M cpu/32 185:09  1.59% postgres
 28199 postgres   1   0    0 3178M 3172M cpu/11  41:52  1.59% postgres
 20361 postgres   1   0    0 3180M 3174M cpu/46 201:25  1.59% postgres
  3768 postgres   1   0    0 3179M 3172M cpu/51  42:47  1.59% postgres
  5410 postgres   1   0    0 3180M 3174M cpu/19 129:45  1.58% postgres
  8183 postgres   1   0    0 3181M 3175M cpu/63 397:59  1.58% postgres
 20472 postgres   1   0    0 3181M 3174M cpu/38 191:32  1.57% postgres
 22793 postgres   1   0    0 3181M 3175M sleep  155:57  1.54% postgres
 27811 postgres   1   0    0 3179M 3173M cpu/7   61:28  1.50% postgres
  3770 postgres   1   0    0 3176M 3170M cpu/59  26:25  1.29% postgres
  9473 postgres   1   0    0 3167M 3162M cpu/14   6:44  1.16% postgres
 19994 postgres   1  50    0 3179M 3173M sleep   81:53  1.10% postgres
  2773 postgres   1   0    0 3162M 3157M cpu/1   32:07  1.08% postgres
  6356 postgres   1   0    0 3180M 3174M cpu/2  130:16  0.64% postgres