Hi Ming-Lei - What I like about your explanation is it allows cache status to be the communication path for network traffic to impact the issue, ie network activity finally spills the cache that does update the qtd descriptor and then we get less deadtime. That sounds very good to me.
I'm using this tree http://git.linaro.org/gitweb?p=people/andygreen/kernel- tilt.git;a=patch;h=7021a2ea35d0b0f96e6c5a753312c26466919efd Your patch http://git.linaro.org/gitweb?p=people/andygreen/kernel- tilt.git;a=shortlog;h=refs/heads/tilt-linux-linaro-3.0 I realized I do have a USB HDD here. I will try that as well in case the USB flash drive is the limiting factor. -- 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
