portupgrade causes kernel message: maxproc limit exceeded by uid 0

[Yuri]

Beginning at some time less than 1 month ago I started getting such 
message. Increasing maxproc doesn't help. Current values are like this:
kern.maxproc: 6164
kern.maxprocperuid: 5547

What may be causing such condition?

Yuri

--- sample log from portupgrade ---
mv -f .deps/regex.Tpo .deps/regex.Po
/bin/sh /usr/ports/devel/glib20/work/gnome-libtool  --tag=CC   
--mode=link cc  -O2 -pipe -fno-strict-aliasing -Wall  -L/usr/local/lib 
-lintl -o markup-escape markup-escape.o ../../glib/libglib-2.0.la
mv -f .deps/gdatetime.Tpo .deps/gdatetime.Po
/bin/sh /usr/ports/devel/glib20/work/gnome-libtool  --tag=CC   
--mode=link cc  -O2 -pipe -fno-strict-aliasing -Wall  -L/usr/local/lib 
-lintl -o markup-subparser markup-subparser.o ../../glib/libglib-2.0.la
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
/printf: Cannot fork: Resource temporarily unavailable
./printf: Cannot fork: Resource temporarily unavailable
cd: can't cd to /snprintf
/snprintf
/snprintf
/snprintf
/snprintf
/snprintf
/snprintf
/printf
/printf
/printf
/sprintf

GLib-ERROR **: failed to fork test program: Resource temporarily unavailable
aborting...

GLib-ERROR **: failed to fork test program: Resource temporarily unavailable
aborting...
cd: can't cd to /snprintf
/snprintf
/snprintf
/snprintf
/snprintf
/snprintf