Re: [RFC/T/D][PATCH 2/2] Linux/Guest cooperative unmapped page cachecontrol

From: Avi Kivity
Date: Thu Jun 10 2010 - 05:43:21 EST

On 06/08/2010 06:51 PM, Balbir Singh wrote:
Balloon unmapped page cache pages first

From: Balbir Singh<balbir@xxxxxxxxxxxxxxxxxx>

This patch builds on the ballooning infrastructure by ballooning unmapped
page cache pages first. It looks for low hanging fruit first and tries
to reclaim clean unmapped pages first.

I'm not sure victimizing unmapped cache pages is a good idea. Shouldn't page selection use the LRU for recency information instead of the cost of guest reclaim? Dropping a frequently used unmapped cache page can be more expensive than dropping an unused text page that was loaded as part of some executable's initialization and forgotten.

Many workloads have many unmapped cache pages, for example static web serving and the all-important kernel build.

The key advantage was that it resulted in lesser RSS usage in the host and
more cached usage, indicating that the caching had been pushed towards
the host. The guest cached memory usage was lower and free memory in
the guest was also higher.

Caching in the host is only helpful if the cache can be shared, otherwise it's better to cache in the guest.

error compiling committee.c: too many arguments to function

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