virtually no free memory left on buildworld

I just installed new 4GB RAM in ia64 rx2600 box.
On make -j8 buildworld I see with "top -PISu":


last pid: 69791;  load averages:  8.42,  8.44,  8.59    up 0+02:04:49  18:18:17
154 processes: 11 running, 125 sleeping, 18 waiting
CPU 0: 88.8% user,  0.0% nice, 11.0% system,  0.1% interrupt,  0.0% idle
CPU 1: 92.5% user,  0.0% nice,  7.4% system,  0.0% interrupt,  0.0% idle
Mem: 856M Active, 2414M Inact, 492M Wired, 136M Cache, 417M Buf, 17M Free
Swap: 2048M Total, 2048M Free

  PID    UID    THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
63039      0      1 102    0   455M   452M RUN     1   3:14 31.49% cc1
69612      0      1 101    0 71760K 69288K RUN     1   0:06 25.88% cc1
69449      0      1 101    0   103M   101M RUN     0   0:11 24.46% cc1
69437      0      1 101    0   115M   113M RUN     0   0:11 23.88% cc1
69626      0      1 100    0 66688K 64760K RUN     0   0:05 20.36% cc1
69774      0      1  96    0 23072K 21336K RUN     0   0:00  4.69% cc1
69775      0      1  70    0  4296K  2984K piperd  0   0:00  0.20% as
69772      0      1  76    0  6280K  2896K wait    1   0:00  0.10% sh
69773      0      1  76    0  2248K   968K wait    1   0:00  0.10% cc
69784      0      1  96    0 19104K 16872K CPU1    1   0:00  0.00% cc1
69785      0      1  76    0  4296K  2968K piperd  1   0:00  0.00% as


Is it normal that there is virtually no free memory left, while there
are 2GB of inactive memory?

many thanks

-- 
Anton Shterenlikht
Room 2.6, Queen's Building
Mech Eng Dept
Bristol University
University Walk, Bristol BS8 1TR, UK
Tel: +44 (0)117 928 8233 
Fax: +44 (0)117 929 4423