Ah! /dev/urandom is the limiting factor ^^ USB HDD is also stuck at 1.9Mbps with the same test. Same test with of=/dev/null is only getting 2.0Mbps.
With the USB HDD and if=/dev/zero instead, and 10x count root@linaro:~# dd if=/dev/zero of=/media/dump bs=40960 count=10000 10000+0 records in 10000+0 records out 409600000 bytes (410 MB) copied, 16.5168 s, 24.8 MB/s root@linaro:~# dd if=/dev/zero of=/media/dump bs=40960 count=10000 10000+0 records in 10000+0 records out 409600000 bytes (410 MB) copied, 18.4294 s, 22.2 MB/s With the patch out, this takes an insanely long time. Against the USB stick, it rises to 7.1MBps with the patch in vs 3.5MBps with it out. So nice job! -- 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: ARM SMP scheduler performance bug Status in Linaro Ubuntu Evaluation Builds: Confirmed Status in Linaro Linux: Confirmed Status in OEM Priority Project: New Status in “linux-ti-omap4” package in Ubuntu: Confirmed Status in “linux-ti-omap4” source package in Maverick: Confirmed Status in “linux-ti-omap4” source package in Natty: Confirmed Status in “linux-ti-omap4” source package in Oneiric: Confirmed Bug description: Original Bug name: "panda: USB disk IO slow" This bug effects ARM Cortex A9 cores, snowball, nvidia, OMAP 4, and other Cortex A9 processors. Problem is in Fedora ARM builds also so not limited to Ubuntu. 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
