Re: [RFC] respect the referenced bit of KVM guest pages?

[Avi Kivity <avi@redhat.com>]

On 08/06/2009 01:59 PM, Wu Fengguang wrote:
>
> This is a quick hack to materialize the idea. It remembers roughly
> the last 32*SWAP_CLUSTER_MAX=1024 active (mapped) pages scanned,
> and if _all of them_ are referenced, then the referenced bit is
> probably meaningless and should not be taken seriously.
>
>    

I don't think we should ignore the referenced bit. There could still be 
a large batch of unreferenced pages later on that we should 
preferentially swap. If we swap at least 1 page for every 250 scanned, 
after 4K swaps we will have traversed 1M pages, enough to find them.

> As a refinement, the static variable 'recent_all_referenced' could be
> moved to struct zone or made a per-cpu variable.
>
>    

Definitely this should be made part of the zone structure, consider the 
original report where the problem occurs in a 128MB zone (where we can 
expect many pages to have their referenced bit set).

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