It's a combination of bugs in the kernel and X server (Xsgi) which
  result in leaked memory being allocated to Xsgi. Its total size (but
  not its resident size) increases until swap space is completely
  filled. It is fixed by the combination of patches 1187 (for non-Impact
  graphics) or 1098 (for Impact graphics) and 1255 for IRIX 5.3.

  You might also add the following to /usr/bin/X11/X before the lines
  where it starts Xsgi

    MALLOC_CONFIG=2:mm_minunmapsrch=0:mm_xf[0].mm_flindx=7:mm_xf[0].mm_szshft=5:mm_xf[1].mm_flindx=2055:mm_xf[1].mm_szshft=8:mm_xf[2].mm_flindx=2065:mm_xf[2].mm_szshft=20:mm_flsearh=30:mm_missthrash=4:mm_nszmult=32
    export MALLOC_CONFIG

  (two lines, one beginning with "MALLOC_CONFIG=" and one with
  "export") or restart Xsgi periodically by hand or at each logout as
  described above.

Some parts © 2009 Advameg, Inc.