Ghostscript appears to hang processing tests/ps/imagemask-with-pattern.ps with
-dDOINTERPOLATE and -r600. It's not clear if it's an actual hang, or just taking
forever. Michael says it never leaves s_imscale_process.

This command line completes on my machine (x86_64) in 1.2 seconds:

bin/gs -Ilib -sDEVICE=ppmraw -o foo.ppm -r600 ../tests/ps/imagemask-with-pattern.ps 

This command line completes on the same machine in 715 seconds:

bin/gs -Ilib -sDEVICE=ppmraw -o bar.ppm -r600 -dDOINTERPOLATE
../tests/ps/imagemask-with-pattern.ps

This command hasn't completed on a 'green' cluster node after 7500 seconds:

./bin/gs -q -I$HOME/fonts -dQUIET -dSAFER -dNOPAUSE -dBATCH -K1000000
-dMaxBitmap=30000000 -dDOINTERPOLATE -sDEVICE=ppmraw -r600
-sOutputFile="|md5sum>/tmp/imagemask-with-pattern.ps.md5" -dJOBSERVER - <
/b/02/atfxsw01/tests_public/ps/imagemask-with-pattern.ps