linux-kernel - Re: [RFC][PATCH 4/9] create aggregate kvm_total_used_mmu

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Message-ID: <4C19E023.2040403@redhat.com>
Date:	Thu, 17 Jun 2010 11:43:15 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [RFC][PATCH 4/9] create aggregate kvm_total_used_mmu_pages value

On 06/16/2010 06:06 PM, Dave Hansen wrote:
>
>
>>> +static inline void kvm_mod_used_mmu_pages(struct kvm *kvm, int nr)
>>> +{
>>> +	kvm->arch.n_used_mmu_pages += nr;
>>> +	kvm_total_used_mmu_pages += nr;
>>>
>>>        
>> Needs an atomic operation, since there's no global lock here.  To avoid
>> bouncing this cacheline around, make the variable percpu and make
>> readers take a sum across all cpus.  Side benefit is that you no longer
>> need an atomic but a local_t, which is considerably cheaper.
>>      
> That's a good point.  All of the modifications are done under locks, but
> the fast path isn't any more.  I'll fix it up.
>
>    

Note, even before you moved the shrinker out of the lock, this was a 
problem.  kvm_mod_used_mmu_pages() is called not just from the shrinker 
code, we zap pages for other reasons as well.

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

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