Re: [PATCH 06/10] ksm: identify PageKsm pages

From: Hugh Dickins
Date: Thu Jul 23 2009 - 07:43:43 EST


On Thu, 23 Jul 2009, KAMEZAWA Hiroyuki wrote:
> On Wed, 22 Jul 2009 13:54:06 +0100 (BST)
> Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx> wrote:
> >
> > (At this instant I've forgotten why there's an unevictable list at
> > all - somewhere in vmscan.c which is accustomed to dealing with
> > pages on lists, so easier to have them on a list than not?)
> >
> I forget, too. But in short thinking, Unevictable pages should be
> on LRU (marked as PG_lru) for isolating page (from LRU) called by
> page migration etc.
>
> isolate_lru_page()
> -> put page on private list
> -> do some work
> -> putback_lru_page()
>
> sequence is useful at handling pages in a list.
> Because mlock/munclock can be called arbitrarily, unevicatable lru
> works enough good for making above kinds of code simpler.

Yes, I think that's it, thanks.

And for the moment, the KSM pages are therefore unmigratable
as well as unswappable; but that should change in 2.6.33.

Hugh
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