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Re: [Qemu-devel] [PATCH] kvm: rename HINTS_DEDICATED to KVM_HINTS_REALTI
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From: |
Paolo Bonzini |
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Subject: |
Re: [Qemu-devel] [PATCH] kvm: rename HINTS_DEDICATED to KVM_HINTS_REALTIME |
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Date: |
Fri, 18 May 2018 19:17:43 +0200 |
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User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.7.0 |
On 18/05/2018 18:04, Eduardo Habkost wrote:
>> Without mlock you should always use pv spinlocks.
>>
>> Otherwise you risk blocking on a lock taken by
>> a VCPU that is in turn blocked on IO, where the IO
>> is not completing because CPU is being used up
>> spinning.
>
> So the stronger guarantee seems necessary.
>
> Now what should host userspace do if the user is trying to run an
> existing configuration where the CPUID hint was set but memory is
> not pinned?
As mentioned elsewhere in the thread, there are many ways to pin memory,
and mlock is not always necessary. However, I agree with Michael in
making the hint provide a stronger guarantee.
Paolo