aa-200-active_page_swapout

aa-200-active_page_swapout

[Andrew Morton]

Last one.


Don't bother checking for active pages in the swapout path.

Not sure about this one.  Clearly the page isn't *likely* to be on the
active list, because the caller found it on the inactive list.  But I
don't see any locking which would prevent the page from getting bumped
up to the active list in the meanwhile.

Needs more explanation.


=====================================

--- 2.4.19-pre3/mm/vmscan.c~aa-200-active_page_swapout	Tue Mar 19 19:49:04 2002
+++ 2.4.19-pre3-akpm/mm/vmscan.c	Tue Mar 19 19:49:04 2002
@@ -83,10 +83,6 @@ static inline int try_to_swap_out(struct
 		return 0;
 	}
 
-	/* Don't bother unmapping pages that are active */
-	if (PageActive(page))
-		return 0;
-
 	/* Don't bother replenishing zones not under pressure.. */
 	if (!memclass(page_zone(page), classzone))
 		return 0;

-

Re: aa-200-active_page_swapout

[Rik van Riel]

On Tue, 19 Mar 2002, Andrew Morton wrote:

> Don't bother checking for active pages in the swapout path.
>
> Not sure about this one.  Clearly the page isn't *likely* to be on the
> active list, because the caller found it on the inactive list.

Mmmm nope.

The caller of swap_out (shrink_caches) may have been scanning the
inactive list, but swap_out itself scans the page tables.

This means it can encounter all kinds of pages, active, inactive
and even reserved pages.

> --- 2.4.19-pre3/mm/vmscan.c~aa-200-active_page_swapout	Tue Mar 19 19:49:04 2002
> +++ 2.4.19-pre3-akpm/mm/vmscan.c	Tue Mar 19 19:49:04 2002
> @@ -83,10 +83,6 @@ static inline int try_to_swap_out(struct
>  		return 0;
>  	}
>
> -	/* Don't bother unmapping pages that are active */
> -	if (PageActive(page))
> -		return 0;
> -
>  	/* Don't bother replenishing zones not under pressure.. */
>  	if (!memclass(page_zone(page), classzone))
>  		return 0;
>
> -
> -
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Rik
-- 
Bravely reimplemented by the knights who say "NIH".

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Re: aa-200-active_page_swapout

[Andrew Morton]

Rik van Riel wrote:
> 
> On Tue, 19 Mar 2002, Andrew Morton wrote:
> 
> > Don't bother checking for active pages in the swapout path.
> >
> > Not sure about this one.  Clearly the page isn't *likely* to be on the
> > active list, because the caller found it on the inactive list.
> 
> Mmmm nope.
> 
> The caller of swap_out (shrink_caches) may have been scanning the
> inactive list, but swap_out itself scans the page tables.
> 
> This means it can encounter all kinds of pages, active, inactive
> and even reserved pages.
> 

good point :)

So what does the patch do?

-