linaro-release team mailing list archive
-
linaro-release team
-
Mailing list archive
-
Message #00406
[Bug 709245] Re: panda: USB disk IO slow
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 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