lkml.org 
[lkml]   [2006]   [Mar]   [15]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateWed, 15 Mar 2006 22:50:20 +0100
FromIngo Molnar <>
SubjectRe: libata/sata_nv latency on NVIDIA CK804 [was Re: AMD64 X2 lost ticks on PM timer]
* Bill Rugolsky Jr. <brugolsky@telemetry-investments.com> wrote:

>    <...>-2913  0d.h.    8us : raise_softirq_irqoff (blk_complete_request)
>    <...>-2913  0d.h.    8us : __ata_qc_complete (ata_qc_complete)
>    <...>-2913  0d.h.    9us : ata_host_intr (nv_interrupt)
>    <...>-2913  0d.h.    9us!: ata_bmdma_status (ata_host_intr)
>    <...>-2913  0d.h. 16641us : nv_check_hotplug_ck804 (nv_interrupt)
>    <...>-2913  0d.h. 16642us : _spin_unlock_irqrestore (nv_interrupt)
>    <...>-2913  0d.h. 16642us : smp_apic_timer_interrupt (apic_timer_interrupt)
>    <...>-2913  0d.h. 16642us : exit_idle (smp_apic_timer_interrupt)

ouch. The codepath in question (ata_host_intr()) doesnt seem to have any 
loop that could take 16.6 msecs (!). This very much looks like some 
hardware-triggered delay - some really screwed up DMA prioritization 
perhaps, starving the host CPU for 16.6 msecs? But what DMA takes 16.6 
msecs? That's enough time to transfer dozens of megabytes of data on a 
midrange system.

	Ingo
-
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: 2006-03-15 22:11    [from the cache]
©2003-2008