On Tuesday 10 January 2012 16:17:54 wwp wrote:
> Hello there,
>
>
> since I installed CentOS6 few months ago (kept up-to-date using yum),
> I'm facing very poor performances when writing to USB pendrives.
>
> The hardware: a Dell Latitude E6500 laptop (Intel Core Duo P8600
> @2.40Ghz), 4Go RAM + 4Go swap, several USB2 pendrives of various brands
> (less than old, all formatted as vfat).
>
>
> When I perform a copy (with cp or midnight commander, copying big AVI
> files between 300Mo to 1.4Go) to those devices, whatever the source is
> on the same device or on another disk, I notice that the CPU activity
> shows 2 phases as far as I can see with the Gnome system monitor applet:
>
> - a phase where both CPUs show less than 20% of activity, and IOWait
> is <80%. It lasts the time I would expect such copy to last (say,
> it's like writing at 1-4MB/sec to such devices, which is reasonable
> or expected).
>
> - a phase, at least twice as long as 1st phase but this ratio depends
> on the file copy size, where CPUs show <5% of activity but IOWait is
> at 100%.
>
> During phase 1, system and applications are responsive, as expected
> during a file copy to external USB2 disks. During phase 2, system is
> slow, applications are often non responsive.
>
> I was not facing this behaviour w/ Fedora 11, not w/ the Windows XP
> system also installed on this laptop.
>
> I'm not facing such poor performances when writing to externals SATA
> drives (thru the same USB2 ports), even formatted as vfat. Neither when
> writing to those pendrives from another hardware system.
>
> `hdparm -tT` is useless here.
>
> I wonder if some mount options aren't wrong with USB pendrives, see:
> /dev/sdd1 on /media/monolith type vfat (rw,nosuid,nodev,uhelper=udisks,shortname=mixed,dmask=0077,utf8=1,flush)
> my suspicion is about the flush option, which I find atypical here.
>
> BTW, I'm still unable to control the mount options that are
> automatically set by Gnome - even if I can mount manually if I want.
>
> Any hint?
>
>
> Regards,
>
>
There's been a loooong discussion in various threads in Archlinux. For example:
https://bbs.archlinux.org/viewtopic.php?id=112846
A solution could be
"echo madvise > /sys/kernel/mm/transparent_hugepage/defrag"
from:
https://bbs.archlinux.org/viewtopic.php?pid=1033648#p1033648
Because trying:
"echo never > /sys/kernel/mm/transparent_hugepage/defrag"
Might break hibernation/suspending
Notice: havent tested this things in CentOS ;)
Regards
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