lkml.org 
[lkml]   [2007]   [Jan]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: prioritize PCI traffic ?


    Soeren Sonnenburg wrote:
    > On Mon, 2007-01-15 at 19:23 +0530, Vaidyanathan Srinivasan wrote:
    >> Soeren Sonnenburg wrote:
    >>> Dear all,
    >>>
    >>> is it possible to explicitly tell the kernel to prioritize PCI traffic
    >>> for a number of cards in pci slots x,y,z ?
    >>>
    >>> I am asking as severe ide traffic causes lost frames when watching TV
    >>> using 2 DVB cards + vdr... This is simply due to the fact that the PCI
    >>> bus is saturated...
    >> How do you know that the bus is saturated?
    >
    > I simply dd if=/dev/sd? of=/dev/null from four brand new sata-harddisks.
    >
    >> Are you streaming data to/from the ide hard disks/CDROM?
    >
    > yes.
    >
    >> Do you have DMAs 'ON' for the hard disks?
    >
    > yes.

    Good.

    >> Is everything just fine if there are no IDE traffic?
    >
    > yes.

    Good.

    >> Are you running 2.6 kernel with preempt 'ON'?
    >
    > no: CONFIG_PREEMPT_NONE=y
    >

    Try CONFIG_PREEMPT=y it may help. It made the system more responsive
    for me.

    >> Are all hardware on the same IRQ line? (shared interrupts)
    >
    > no: libata devices are on IRQ 16 and DVB devices on IRQ 20

    Watch the interrupt count (/proc/interrupts) and interrupt rate,
    that may give some clue on what is happening on the PCI bus.

    >
    >>> So, is any prioritizing of the PCI bus possible ?
    >> The drivers + application indirectly can control priority on the
    >> bus. Just reduce the priority of the application that uses IDE and
    >> see if adjusting nice values of applications can change the scenario.
    >
    > That unfortunately did not help... no change...

    33Mhz 32-bit PCI bus on typical PC can do around 100MB/sec... watch
    your individual disk transfer rates and data rate to each DVB.
    dd from 4 new SATA drive will probably fillup the bus. However,
    depending on your motherboard, the integrated SATA controllers may
    be on a different PCI bus than the one for the slots.

    You can watch the lspci output to determine which bus the devices
    are located.

    --Vaidy

    >
    > Soeren
    > --
    > Sometimes, there's a moment as you're waking, when you become aware of
    > the real world around you, but you're still dreaming.
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-01-15 16:53    [W:0.025 / U:1.840 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site