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docs: virt: guest-halt-polling.txt convert to ReST
Due to some merge conflict, this file ended being alone under
Documentation/virtual.
The file itself is almost at ReST format. Just minor
adjustments are needed:
- Adjust title markup;
- Adjust a list identation;
- add a literal block markup;
- Add some blank lines.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
authored by
Mauro Carvalho Chehab
and committed by
Paolo Bonzini
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Documentation/virt/guest-halt-polling.rst
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==================
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Guest halt polling
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==================
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The cpuidle_haltpoll driver, with the haltpoll governor, allows
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the guest vcpus to poll for a specified amount of time before
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halting.
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This provides the following benefits to host side polling:
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1) The POLL flag is set while polling is performed, which allows
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The haltpoll governor has 5 tunable module parameters:
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1) guest_halt_poll_ns:
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Maximum amount of time, in nanoseconds, that polling is
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performed before halting.
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Default: 200000
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2) guest_halt_poll_shrink:
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Division factor used to shrink per-cpu guest_halt_poll_ns when
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wakeup event occurs after the global guest_halt_poll_ns.
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Default: 2
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3) guest_halt_poll_grow:
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Multiplication factor used to grow per-cpu guest_halt_poll_ns
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when event occurs after per-cpu guest_halt_poll_ns
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but before global guest_halt_poll_ns.
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Default: 2
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4) guest_halt_poll_grow_start:
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The per-cpu guest_halt_poll_ns eventually reaches zero
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in case of an idle system. This value sets the initial
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per-cpu guest_halt_poll_ns when growing. This can
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Default: Y
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The module parameters can be set from the debugfs files in:
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The module parameters can be set from the debugfs files in::
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/sys/module/haltpoll/parameters/
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···
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=============
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- Care should be taken when setting the guest_halt_poll_ns parameter as a
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large value has the potential to drive the cpu usage to 100% on a machine which
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would be almost entirely idle otherwise.
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large value has the potential to drive the cpu usage to 100% on a machine
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which would be almost entirely idle otherwise.