linux-kernel - Re: [PATCH v5 08/12] Inject asynchronous page fault into a guest if page is swapped out.

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Message-ID: <4C738B23.6040205@redhat.com>
Date:	Tue, 24 Aug 2010 12:04:35 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Gleb Natapov <gleb@...hat.com>
CC:	kvm@...r.kernel.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, mingo@...e.hu,
	a.p.zijlstra@...llo.nl, tglx@...utronix.de, hpa@...or.com,
	riel@...hat.com, cl@...ux-foundation.org, mtosatti@...hat.com
Subject: Re: [PATCH v5 08/12] Inject asynchronous page fault into a guest
 if page is swapped out.

  On 08/24/2010 10:52 AM, Gleb Natapov wrote:
>> This nice cache needs to be outside apf to reduce complexity for
>> reviewers and since it is useful for others.
>>
>> Would be good to have memslot-cached kvm_put_guest() and kvm_get_guest().
> Will look into it.

In the meantime, you can just drop the caching.


>>> +		       struct kvm_arch_async_pf *arch)
>>> +{
>>> +	struct kvm_async_pf *work;
>>> +
>>> +	if (vcpu->async_pf_queued>= ASYNC_PF_PER_VCPU)
>>> +		return 0;
>> 100 == too high.  At 16 vcpus, this allows 1600 kernel threads to
>> wait for I/O.
> Number of kernel threads are limited by other means. Slow work subsystem
> has its own knobs to tune that. Here we limit how much slow work items
> can be queued per vcpu.

OK.

>> Would have been best if we could ask for a page to be paged in
>> asynchronously.
>>
> You mean to have core kernel facility for that? I agree it would be
> nice, but much harder.

Yes, that's what I meant.

-- 
error compiling committee.c: too many arguments to function

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