Results without background task:
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 15.9036 s, 2.1 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 17.1338 s, 2.0 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 16.1808 s, 2.1 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 9.517 s, 3.5 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 9.32068 s, 3.6 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 9.46927 s, 3.5 MB/s
Results with ping -i.01
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 7.64636 s, 4.4 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 8.62585 s, 3.9 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 8.33698 s, 4.0 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 4.49344 s, 7.5 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 4.46146 s, 7.5 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 4.46329 s, 7.5 MB/s
PING localhost (127.0.0.1) 56(84) bytes of data.

--- localhost ping statistics ---
2437 packets transmitted, 2437 received, 0% packet loss, time 38059ms
rtt min/avg/max/mdev = 0.000/0.024/0.092/0.014 ms
Results with ping -i.0099
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 4.11252 s, 8.2 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 3.25732 s, 10.3 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 3.18637 s, 10.5 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 2.03088 s, 16.5 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 1.96857 s, 17.0 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 2.10437 s, 15.9 MB/s
PING localhost (127.0.0.1) 56(84) bytes of data.

--- localhost ping statistics ---
1857 packets transmitted, 1857 received, 0% packet loss, time 16693ms
rtt min/avg/max/mdev = 0.000/0.001/0.061/0.007 ms
Results with perl busy loop
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 17.9713 s, 1.9 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 5.16428 s, 6.5 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 4.53915 s, 7.4 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 3.71222 s, 9.0 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 3.58218 s, 9.4 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 3.97675 s, 8.4 MB/s
./speedtest.sh: line 29:   907 Terminated              perl -e "while (1) { }"
Results with perl usleep(1)
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 6.92044 s, 4.8 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 6.99432 s, 4.8 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 6.63724 s, 5.1 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 3.79697 s, 8.8 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 3.46521 s, 9.7 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 3.78156 s, 8.9 MB/s
./speedtest.sh: line 35:   915 Terminated              perl -e "use Time::HiRes qw( usleep ); while (1) { usleep(1) }"
Results with perl yield
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 6.47668 s, 5.2 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 5.47159 s, 6.1 MB/s
512+0 records in
512+0 records out
33554432 bytes (34 MB) copied, 6.91385 s, 4.9 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 4.08472 s, 8.2 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 7.78119 s, 4.3 MB/s
32+0 records in
32+0 records out
33554432 bytes (34 MB) copied, 6.75308 s, 5.0 MB/s
./speedtest.sh: line 41:   923 Terminated              perl -e "use Thread qw( yield ); while (1) { yield }"