memory allocators. this fixes a bug that caused gdb to crash.. now utest gets good scalability for random add/remove operations on a 1024-element crange: nickolai@ben:~/proj/xv6$ for n in 1 2 4 8 16 32 64 80; do ( time ./o.user/utest -n $n ) 2>&1 | grep ^real | awk '{print "'$n'", $2;}'; done 1 0m21.570s 2 0m16.342s 4 0m9.997s 8 0m5.484s 16 0m3.218s 32 0m1.978s 64 0m1.741s 80 0m1.814s nickolai@ben:~/proj/xv6$