RE: [PATCH] mm: implement WasActive page flag (for improvingcleancache)

[Dan Magenheimer]

> From: Rik van Riel [mailto:riel@xxxxxxxxxx]
> Subject: Re: [PATCH] mm: implement WasActive page flag (for improving cleancache)
> 
> On 01/26/2012 09:43 PM, Dan Magenheimer wrote:
> 
> > Maybe the Active page bit could be overloaded with some minor
> > rewriting?  IOW, perhaps the Active bit could be ignored when
> > the page is moved to the inactive LRU?  (Confusing I know, but I am
> > just brainstorming...)
> 
> The PG_referenced bit is already overloaded.  We keep
> the bit set when we move a page from the active to the
> inactive list, so a page that was previously active
> only needs to be referenced once to become active again.
> 
> The LRU bits (PG_lru, PG_active, etc) are needed to
> figure out which LRU list the page is on.  I don't
> think we can overload those...

I suspected that was true, but was just brainstorming.
Thanks for confirming.

Are there any other page bits that are dont-care when
a page is on an LRU list?

I'd also be interested in your/RedHat's opinion on the
64-bit vs 32-bit market.  Will RHEL7 even support 32-bit?

Dan

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