When running just dd at 1MB block size, I get ~5.5MB/s. When running with sudo ping -q -i.0100 localhost in the background, ping causes 1% CPU load, and I get ~10MB/s at 1MB block size and these ping statistics: 6228 packets transmitted, 6227 received, 0% packet loss, time 97329ms rtt min/avg/max/mdev = 0.000/0.053/2.899/0.050 ms
When running with sudo ping -q -i.0099 localhost in the background, ping causes 100% (one core) CPU load, and I get ~20MB/s at 1MB block size and these ping statistics: 10339 packets transmitted, 10337 received, 0% packet loss, time 93032ms rtt min/avg/max/mdev = 0.000/0.033/0.946/0.031 ms Now why does ping process about twice as many packets but use 100 times more CPU (and get better response times) when I reduce the delay by just one percent? There's something fishy going on here... -- You received this bug notification because you are a member of Linaro Release Team, which is subscribed to the bug report. https://bugs.launchpad.net/bugs/709245 Title: panda: USB disk IO slow Status in Linaro Ubuntu Evaluation Builds: Confirmed Status in Linaro Linux: Confirmed Status in “linux-ti-omap4” package in Ubuntu: Confirmed Status in “linux-ti-omap4” source package in Oneiric: Confirmed Bug description: My Panda's USB seems to be significantly slower than a Beagle C4. hdparm shows buffered reads as ~12MB/s on the Panda, and about ~20-25MB/s on a Beagle C4 from the same external Lacie USB disk. Kernel is 2.6.37-1002-linaro-omap Disk shows as: [ 5.170440] scsi 0:0:0:0: Direct-Access LaCie d2 quadra PQ: 0 ANSI: 4 [ 5.172546] sd 0:0:0:0: Attached scsi generic sg0 type 0 [ 5.175415] sd 0:0:0:0: [sda] 976773168 512-byte logical blocks: (500 GB/465 GiB) The board is otherwise idle during the test. Doing perf_2.6.37-12 record -a dd if=/dev/sda of=/dev/null bs=4096 count=100000 shows : 81.41% swapper [kernel.kallsyms] [k] default_idle 6.33% dd [kernel.kallsyms] [k] __copy_to_user 0.94% swapper [kernel.kallsyms] [k] cpu_idle 0.51% dd [kernel.kallsyms] [k] __make_request 0.51% perf_2.6.37-12 [kernel.kallsyms] [k] __copy_from_user which suggests it's not CPU constrained. Dave To manage notifications about this bug go to: https://bugs.launchpad.net/linaro-ubuntu/+bug/709245/+subscriptions _______________________________________________ Mailing list: https://launchpad.net/~linaro-release Post to : [email protected] Unsubscribe : https://launchpad.net/~linaro-release More help : https://help.launchpad.net/ListHelp
