Further testing points towards thread switching behavior being related: Nothing running in parallel: <10MB/s at big block sizes perl -e "while (1) { }": <5MB/s perl -e "use Time::HiRes qw( usleep ); while (1) { usleep(1) }": 20-25MB/s perl -e "use Time::HiRes qw( nanosleep ); while (1) { nanosleep(1) }": 5-25MB/s (varying widely over time) perl -e "use Thread qw( yield ); while (1) { yield }": 10-20MB/s sudo ping -q -i.001 localhost: 25MB/s (consistently)
Note that the sleep variants only reach ~25% CPU load (as seen in top), while the yield and ping variants use a full core. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/709245 Title: panda: USB disk IO slow To manage notifications about this bug go to: https://bugs.launchpad.net/linaro-ubuntu/+bug/709245/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs