[Xen-devel] [PATCH v3 0/6] prevent Qemu from waking up needlessly

[Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>]

Hi all,
this small patch series prevents Qemu from waking up needlessly on Xen
several times a second in order to check some timers.



The first patch stops Qemu from emulating the PIT on Xen, the second
patch disables the rtc_clock entirely.

The third patch makes use of a new mechanism to receive buffered io
event notifications from Xen, so that Qemu doesn't need to check the
buffered io page for data 10 times a sec for the entire life of the VM.

The fourth patch fixes win32_rearm_timer and mm_rearm_timer that
risk an overflow if INT64_MAX is passed as delta.

The fifth patch changes qemu_next_alarm_deadline only to check the
expire time of a clock if it is enabled.

Finally the last patch increases the default select timeout to 1h:
nothing should rely on the select timeout to be 1sec, so we might as
well increase it to 1h.



Changes in v3:

- added a new patch to fix win32_rearm_timer and mm_rearm_timer, that
risk an overflow if INT64_MAX is passed as delta.




Shortlog and diffstat follow:

Stefano Stabellini (6):
      xen: do not initialize the interval timer emulator
      xen: disable rtc_clock
      xen: introduce an event channel for buffered io event notifications
      timers: the rearm function should be able to handle delta = INT64_MAX
      qemu_next_alarm_deadline: check the expire time of a clock only if it is 
enabled
      qemu_calculate_timeout: increase minimum timeout to 1h

 hw/pc.c      |    7 +++++--
 qemu-timer.c |   30 ++++++++++++++++++------------
 xen-all.c    |   43 +++++++++++++++++++++++++++++++++++++------
 3 files changed, 60 insertions(+), 20 deletions(-)


A git tree available here:

git://xenbits.xen.org/people/sstabellini/qemu-dm.git timers-3

Cheers,

Stefano

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