Re: [PATCH] mm: inactive-clean list

From: Martin Schwidefsky
Date: Wed Jul 26 2006 - 09:02:27 EST

On 7/26/06, Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> wrote:
> Hmm, I wonder how the inactive clean list helps in regard to the fast
> host reclaim
> scheme. In particular since the memory pressure that triggers the
> reclaim is in the
> host, not in the guest. So all pages might be on the active list but
> the host still
> wants to be able to discard pages.

I think Rik would want to set all the already unmapped pages to volatile
state in the hypervisor.

These pages can be dropped without loss of information on the guest
system since they are all already on a backing-store, be it regular
files or swap.

I guessed that as well. It isn't good enough. Consider a guest with a
large (virtual) memory size and a host with a small physical memory
size. The guest will never put any page on the inactive_clean list
because it does not have memory pressure. vmscan will never run. The
host wants to reclaim memory of the guest, but since the
inactive_clean list is empty it will find only stable pages.

blue skies,
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