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Re: [Xen-devel] [PATCH]HVM acpi timer update

  • To: "Wang, Winston L" <winston.l.wang@xxxxxxxxx>
  • From: "Christian Limpach" <christian.limpach@xxxxxxxxx>
  • Date: Thu, 27 Jul 2006 11:36:47 +0100
  • Cc: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx, Tang Liang <tangliang@xxxxxxxxxx>
  • Delivery-date: Thu, 27 Jul 2006 03:37:10 -0700
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On 7/27/06, Wang, Winston L <winston.l.wang@xxxxxxxxx> wrote:
The patch updated the hvm acpi timer by reducing invocations to
timer_update and some minor code style clean up:
1) Fixed new qemu 0.8.1 pm timer incorrect frequency and allow acpi
windows install and boot correctly
2) Resolved performance issues caused by old acpi timer, testing showing
guest IDE DMA and kernel build have the same performance on non-acpi

Why does this still need a timer at all?  Why can't we just compute
the acpi timer's value when it is being read: (get_vm_clock() -
vm_clock_value_when_domain_was_started) divided/multiplied to get the
expected frequency?

Also, since this is using vm_clock, the acpi_timer will advance even
if the domain is not scheduled -- is this the expected behaviour?


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