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Date:   Wed, 30 Aug 2017 09:33:52 +0200
From:   Juergen Gross <>
To:     Konrad Rzeszutek Wilk <>,
        Yang Zhang <>,,
        Boris Ostrovsky <>
        Quan Xu <>,
        Jeremy Fitzhardinge <>,
        Chris Wright <>,
        Alok Kataria <>,
        Rusty Russell <>,
        Ingo Molnar <>,
        "H. Peter Anvin" <>,,
        Andy Lutomirski <>,
        "Kirill A. Shutemov" <>,
        Pan Xinhui <>,
        Kees Cook <>,
Subject: Re: [RFC PATCH v2 1/7] x86/paravirt: Add pv_idle_ops to paravirt ops

On 29/08/17 15:55, Konrad Rzeszutek Wilk wrote:
> On Tue, Aug 29, 2017 at 11:46:35AM +0000, Yang Zhang wrote:
>> So far, pv_idle_ops.poll is the only ops for pv_idle. .poll is called in
>> idle path which will polling for a while before we enter the real idle
>> state.
>> In virtualization, idle path includes several heavy operations
>> includes timer access(LAPIC timer or TSC deadline timer) which will hurt
>> performance especially for latency intensive workload like message
>> passing task. The cost is mainly come from the vmexit which is a
>> hardware context switch between VM and hypervisor. Our solution is to
>> poll for a while and do not enter real idle path if we can get the
>> schedule event during polling.
>> Poll may cause the CPU waste so we adopt a smart polling mechanism to
>> reduce the useless poll.
>> Signed-off-by: Yang Zhang <>
>> Signed-off-by: Quan Xu <>
>> Cc: Jeremy Fitzhardinge <>
>> Cc: Chris Wright <>
>> Cc: Alok Kataria <>
>> Cc: Rusty Russell <>
>> Cc: Thomas Gleixner <>
>> Cc: Ingo Molnar <>
>> Cc: "H. Peter Anvin" <>
>> Cc:
>> Cc: Peter Zijlstra <>
>> Cc: Andy Lutomirski <>
>> Cc: "Kirill A. Shutemov" <>
>> Cc: Pan Xinhui <>
>> Cc: Kees Cook <>
>> Cc:
>> Cc:
> Adding xen-devel.
> Juergen, we really should replace Jeremy's name with xen-devel or
> your name..

I wouldn't mind being added. What does Jeremy think of being removed?

> Wasn't there an patch by you that took some of the 
> mainternship over it?

I added include/linux/hypervisor.h to the PARAVIRT section and offered
to maintain it in case the PARAVIRT maintainers didn't want to.


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