I tested some more today (Oneiric 3.0 kernel) and the external USB drive on a Panda.
With nosmp passed on the boot command line, the throughput is good with or without the ping and about the same as using both cores and pinging it. Booting with both cores and putting cpu1 offline does not seem to affect the behaviour - pinging leads to 4x or 5x throughput over not-pinging. So it may be related to SMP scheduling. Also nosmp and putting one core offline at runtime is apparently not the same ( I naively thought it should be) -- 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
