Re: [PATCH] Replace page_mapping_inuse() with page_mapped()

[Rik van Riel]

On 12/01/2009 10:28 PM, KOSAKI Motohiro wrote:
> > On 12/01/2009 09:55 PM, KOSAKI Motohiro wrote:
> >      
> > > > btw, current shrink_active_list() have unnecessary page_mapping_inuse() call.
> > > > it prevent to drop page reference bit from unmapped cache page. it mean
> > > > we protect unmapped cache page than mapped page. it is strange.
> > > >
> > > >          
> > > How about this?
> > >
> > > ---------------------------------
> > > SplitLRU VM replacement algorithm assume shrink_active_list() clear
> > > the page's reference bit. but unnecessary page_mapping_inuse() test
> > > prevent it.
> > >
> > > This patch remove it.
> > >
> > >        
> > Shrink_page_list ignores the referenced bit on pages
> > that are !page_mapping_inuse().
> >
> >                   if (sc->order<= PAGE_ALLOC_COSTLY_ORDER&&
> >                                           referenced&&
> > page_mapping_inuse(page)
> > &&  !(vm_flags&  VM_LOCKED))
> >                           goto activate_locked;
> >
> > The reason we leave the referenced bit on unmapped
> > pages is that we want the next reference to a deactivated
> > page cache page to move that page back to the active
> > list.  We do not want to require that such a page gets
> > accessed twice before being reactivated while on the
> > inactive list, because (1) we know it was a frequently
> > accessed page already and (2) ongoing streaming IO
> > might evict it from the inactive list before it gets accessed
> > twice.
> >
> > Arguably, we should just replace the page_mapping_inuse()
> > in both places with page_mapped() to simplify things.
> >      
> Ah, yes. /me was slept. thanks correct me.
>
>
>  From 61340720e6e66b645db8d5410e89fd3b67eda907 Mon Sep 17 00:00:00 2001
> From: KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx>
> Date: Wed, 2 Dec 2009 12:05:26 +0900
> Subject: [PATCH] Replace page_mapping_inuse() with page_mapped()
>
> page reclaim logic need to distingish mapped and unmapped pages.
> However page_mapping_inuse() don't provide proper test way. it test
> the address space (i.e. file) is mmpad(). Why `page' reclaim need
> care unrelated page's mapped state? it's unrelated.
>
> Thus, This patch replace page_mapping_inuse() with page_mapped()
>
> Signed-off-by: KOSAKI Motohiro<kosaki.motohiro@xxxxxxxxxxxxxx>
>    
Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>
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