linux-kernel - Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped page cache control

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Message-ID: <4C1727A9.9040606@redhat.com>
Date:	Tue, 15 Jun 2010 10:11:37 +0300
From:	Avi Kivity <avi@...hat.com>
To:	balbir@...ux.vnet.ibm.com
CC:	Dave Hansen <dave@...ux.vnet.ibm.com>, kvm <kvm@...r.kernel.org>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped page cache
 control

On 06/14/2010 08:40 PM, Balbir Singh wrote:
> * Avi Kivity<avi@...hat.com>  [2010-06-14 18:34:58]:
>
>    
>> On 06/14/2010 06:12 PM, Dave Hansen wrote:
>>      
>>> On Mon, 2010-06-14 at 14:18 +0530, Balbir Singh wrote:
>>>        
>>>> 1. A slab page will not be freed until the entire page is free (all
>>>> slabs have been kfree'd so to speak). Normal reclaim will definitely
>>>> free this page, but a lot of it depends on how frequently we are
>>>> scanning the LRU list and when this page got added.
>>>>          
>>> You don't have to be freeing entire slab pages for the reclaim to have
>>> been useful.  You could just be making space so that _future_
>>> allocations fill in the slab holes you just created.  You may not be
>>> freeing pages, but you're reducing future system pressure.
>>>        
>> Depends.  If you've evicted something that will be referenced soon,
>> you're increasing system pressure.
>>
>>      
> I don't think slab pages care about being referenced soon, they are
> either allocated or freed. A page is just a storage unit for the data
> structure. A new one can be allocated on demand.
>    

If we're talking just about slab pages, I agree.  If we're applying 
pressure on the shrinkers, then you are removing live objects which can 
be costly to reinstantiate.


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

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