FAQ
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�77,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,

--
wwp
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  • John Doe at Jan 10, 2012 at 11:57 am
    From: wwp <subscript at free.fr>
    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�77,utf8=1,flush)
    my suspicion is about the flush option, which I find atypical here.
    I guess it is to be safe in case users remove their usb keys without
    unmounting first...

    JD
  • Wwp at Jan 11, 2012 at 2:45 am
    Hello John,

    On Tue, 10 Jan 2012 08:57:14 -0800 (PST) John Doe wrote:

    From: wwp <subscript at free.fr>
    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�77,utf8=1,flush)
    my suspicion is about the flush option, which I find atypical here.
    I guess it is to be safe in case users remove their usb keys without
    unmounting first...
    OK, meaning no write-cache for those devices, makes sense in some
    way. But this doesn't explain the main issue I reported, although I
    didn't find a way to change the default mount options used by Gnome
    (gconf settings don't match those that are used).


    Regards,

    --
    wwp
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  • Ljubomir Ljubojevic at Jan 11, 2012 at 10:31 am

    On 01/11/2012 08:45 AM, wwp wrote:
    Hello John,


    On Tue, 10 Jan 2012 08:57:14 -0800 (PST) John Doewrote:
    From: wwp<subscript at free.fr>
    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�77,utf8=1,flush)
    my suspicion is about the flush option, which I find atypical here.
    I guess it is to be safe in case users remove their usb keys without
    unmounting first...
    OK, meaning no write-cache for those devices, makes sense in some
    way. But this doesn't explain the main issue I reported, although I
    didn't find a way to change the default mount options used by Gnome
    (gconf settings don't match those that are used).
    Do you have ehci_hcd module running?

    Do you have any error messages in dmesg after you plug it in?


    --

    Ljubomir Ljubojevic
    (Love is in the Air)
    PL Computers
    Serbia, Europe

    Google is the Mother, Google is the Father, and traceroute is your
    trusty Spiderman...
    StarOS, Mikrotik and CentOS/RHEL/Linux consultant
  • Wwp at Jan 11, 2012 at 12:42 pm
    Hello Ljubomir,

    On Wed, 11 Jan 2012 16:31:43 +0100 Ljubomir Ljubojevic wrote:
    On 01/11/2012 08:45 AM, wwp wrote:
    Hello John,


    On Tue, 10 Jan 2012 08:57:14 -0800 (PST) John Doewrote:
    From: wwp<subscript at free.fr>
    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�77,utf8=1,flush)
    my suspicion is about the flush option, which I find atypical here.
    I guess it is to be safe in case users remove their usb keys without
    unmounting first...
    OK, meaning no write-cache for those devices, makes sense in some
    way. But this doesn't explain the main issue I reported, although I
    didn't find a way to change the default mount options used by Gnome
    (gconf settings don't match those that are used).
    Do you have ehci_hcd module running?

    Do you have any error messages in dmesg after you plug it in?
    ehci_hcd does manage my devices (it's not a loadable module, apparently
    compiled in kernel instead), see for instance:

    kernel: usb 2-2: new high speed USB device using ehci_hcd and address 28
    kernel: usb 2-2: New USB device found, idVendora5, idProduct00
    kernel: usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
    kernel: usb 2-2: Product: STORE N GO
    kernel: usb 2-2: Manufacturer: Verbatim
    kernel: usb 2-2: SerialNumber: 25LHXEWIZ5IZKSO0
    kernel: usb 2-2: configuration #1 chosen from 1 choice
    kernel: scsi26 : SCSI emulation for USB Mass Storage devices
    kernel: scsi 26:0:0:0: Direct-Access Verbatim STORE N GO 1100 PQ: 0 ANSI: 0 CCS
    kernel: sd 26:0:0:0: Attached scsi generic sg4 type 0
    kernel: sd 26:0:0:0: [sdd] 31506432 512-byte logical blocks: (16.1 GB/15.0 GiB)
    kernel: sd 26:0:0:0: [sdd] Write Protect is off
    kernel: sd 26:0:0:0: [sdd] Assuming drive cache: write through
    kernel: sd 26:0:0:0: [sdd] Assuming drive cache: write through
    kernel: sdd: sdd1
    kernel: sd 26:0:0:0: [sdd] Assuming drive cache: write through
    kernel: sd 26:0:0:0: [sdd] Attached SCSI removable disk

    No error AFAICS.


    Regards,

    --
    wwp
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  • Mark Roth at Jan 11, 2012 at 1:33 pm
    Blah, blah, blah,

    Being blocked again, still appears to be based on new content vs. included
    content.

    Which makes it very annoying when I want to include context for my response.

    blah, blah, blah, new content.................

    Hi, wwp,

    wwp wrote:
    On Wed, 11 Jan 2012 16:31:43 +0100 Ljubomir Ljubojevic wrote:
    On 01/11/2012 08:45 AM, wwp wrote:
    On Tue, 10 Jan 2012 08:57:14 -0800 (PST) John Doe<jdmls at yahoo.com>
    wrote:
    From: wwp<subscript at free.fr>
    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�77,utf8=1,flush)
    my suspicion is about the flush option, which I find atypical here.
    <snip>
    ehci_hcd does manage my devices (it's not a loadable module, apparently
    compiled in kernel instead), see for instance:
    kernel: usb 2-2: new high speed USB device using ehci_hcd and address 28
    <snip>
    This may be a dumb question, but have you done an lsusb? I'd be curious -
    I know that on my brand new, as of a few months ago, Dell I have two kinds
    of USB ports, 1.1 and 2.0. We also have some 1.1 webcams... and some 1.0.

    See if your pen drive's in a slower port.

    mark
  • Ljubomir Ljubojevic at Jan 11, 2012 at 6:54 pm

    On 01/11/2012 07:33 PM, m.roth at 5-cent.us wrote:
    wwp wrote:
    On Wed, 11 Jan 2012 16:31:43 +0100 Ljubomir Ljubojevicwrote:
    On 01/11/2012 08:45 AM, wwp wrote:
    On Tue, 10 Jan 2012 08:57:14 -0800 (PST) John Doe<jdmls at yahoo.com>
    wrote:
    From: wwp<subscript at free.fr>
    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�77,utf8=1,flush)
    my suspicion is about the flush option, which I find atypical here.
    <snip>
    ehci_hcd does manage my devices (it's not a loadable module, apparently
    compiled in kernel instead), see for instance:
    kernel: usb 2-2: new high speed USB device using ehci_hcd and address 28
    <snip>
    This may be a dumb question, but have you done an lsusb? I'd be curious -
    I know that on my brand new, as of a few months ago, Dell I have two kinds
    of USB ports, 1.1 and 2.0. We also have some 1.1 webcams... and some 1.0.

    See if your pen drive's in a slower port.
    Yes I have seen those too and was VERY surprised.


    --

    Ljubomir Ljubojevic
    (Love is in the Air)
    PL Computers
    Serbia, Europe

    Google is the Mother, Google is the Father, and traceroute is your
    trusty Spiderman...
    StarOS, Mikrotik and CentOS/RHEL/Linux consultant
  • Marc Deop at Jan 12, 2012 at 5:53 am

    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�77,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?id2846

    A solution could be

    "echo madvise > /sys/kernel/mm/transparent_hugepage/defrag"

    from:

    https://bbs.archlinux.org/viewtopic.php?pid33648#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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