cvs fail because allocate memory fail

[Water NB <netbsd78%126.com@localhost>]

My system is :
$ uname -a
NetBSD s1 4.0_STABLE NetBSD 4.0_STABLE (a64nb4) #6: Fri Sep 18 16:07:56
CST 2009
  water@s1:/usr/world/a64o4/sys/arch/amd64/compile/a64nb4 amd64
 
When I check out a binary file from CVS via WinCVS, it report below:
-f [update aborted]: Could not map memory to RCS archive
/home/cvs/MyBinary,v: Cannot allocate memory

I notice /home/cvs/MyBinary,v is a about 300M bytes, it is a binary file
and committed 22 times.


# top
load averages:  0.00,  0.00,  0.00                   up 1 day, 13:09
11:49:23
82 processes:  80 sleeping, 1 zombie, 1 on processor
CPU0 states:     % user,     % nice,     % system,     % interrupt,
% idle
CPU1 states:     % user,     % nice,     % system,     % interrupt,
% idle
Memory: 950M Act, 543M Inact, 2616K Wired, 29M Exec, 1238M File, 276M
Free


$ ulimit
unlimited

I wrote a test program to allocate 256M bytes, it failed.
There are 1238M bytes space for File, 
why can't swap them then when I/CVS allocates.

Thanks.