[PATCH]mm:Correctly update number of rotated pages on active list.

[PATCH]mm:Correctly update number of rotated pages on active list.

[Pradeep Goswami (Pradeep Kumar Goswami)]

This patch corrects the number of pages which are rotated on active list.
The counter for rotated pages effects the number of pages
to be scanned on active pages list in  low memory situations.

Signed-off-by: Pradeep Goswami <pradeep.goswami@spredtrum.com>
Cc: Rebecca Schultz Zavin <rebecca@android.com>
Cc: Vladimir Davydov <vdavydov@parallels.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
---
--- a/mm/vmscan.c       2015-11-18 20:55:38.208838142 +0800
+++ b/mm/vmscan.c       2015-11-19 14:37:31.189838998 +0800
@@ -1806,7 +1806,6 @@ static void shrink_active_list(unsigned
 
                if (page_referenced(page, 0, sc->target_mem_cgroup,
                                    &vm_flags)) {
-                       nr_rotated += hpage_nr_pages(page);
                        /*  
                         * Identify referenced, file-backed active pages and 
                         * give them one more trip around the active list. So
@@ -1818,6 +1817,7 @@ static void shrink_active_list(unsigned
                         */  
                        if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
                                list_add(&page->lru, &l_active);
+                               nr_rotated += hpage_nr_pages(page);
                                continue;
                        }   
                }   

Thanks,
Pradeep.
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Re: [PATCH]mm:Correctly update number of rotated pages on active list.

[Michal Hocko]

On Thu 03-12-15 10:08:11, Pradeep Goswami (Pradeep Kumar Goswami) wrote:
> This patch corrects the number of pages which are rotated on active list.
> The counter for rotated pages effects the number of pages
> to be scanned on active pages list in  low memory situations.

Why this should be changed?

This seems to be deliberate:
        /*
         * Count referenced pages from currently used mappings as rotated,
         * even though only some of them are actually re-activated.  This
         * helps balance scan pressure between file and anonymous pages in
         * get_scan_count.
         */
        reclaim_stat->recent_rotated[file] += nr_rotated;

What kind of problem are you trying to fix?

> 
> Signed-off-by: Pradeep Goswami <pradeep.goswami@spredtrum.com>
> Cc: Rebecca Schultz Zavin <rebecca@android.com>
> Cc: Vladimir Davydov <vdavydov@parallels.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> ---
> --- a/mm/vmscan.c       2015-11-18 20:55:38.208838142 +0800
> +++ b/mm/vmscan.c       2015-11-19 14:37:31.189838998 +0800
> @@ -1806,7 +1806,6 @@ static void shrink_active_list(unsigned
>  
>                 if (page_referenced(page, 0, sc->target_mem_cgroup,
>                                     &vm_flags)) {
> -                       nr_rotated += hpage_nr_pages(page);
>                         /*  
>                          * Identify referenced, file-backed active pages and 
>                          * give them one more trip around the active list. So
> @@ -1818,6 +1817,7 @@ static void shrink_active_list(unsigned
>                          */  
>                         if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
>                                 list_add(&page->lru, &l_active);
> +                               nr_rotated += hpage_nr_pages(page);
>                                 continue;
>                         }   
>                 }   
> 
> Thanks,
> Pradeep.
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-- 
Michal Hocko
SUSE Labs

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Re: [PATCH]mm:Correctly update number of rotated pages on active list.

[Pradeep Goswami (Pradeep Kumar Goswami)]

On Thu, Dec 03, 2015 at 11:59:48AM +0100, Michal Hocko wrote:
> On Thu 03-12-15 10:08:11, Pradeep Goswami (Pradeep Kumar Goswami) wrote:
> > This patch corrects the number of pages which are rotated on active list.
> > The counter for rotated pages effects the number of pages
> > to be scanned on active pages list in  low memory situations.
> 
> Why this should be changed?
> 
> This seems to be deliberate:
>         /*
>          * Count referenced pages from currently used mappings as rotated,
>          * even though only some of them are actually re-activated.  This
>          * helps balance scan pressure between file and anonymous pages in
>          * get_scan_count.
>          */
>         reclaim_stat->recent_rotated[file] += nr_rotated;
> 
> What kind of problem are you trying to fix?
Actually the numeber of pages which are actually rotated are wrongly
updated, So I thought this might be minor coding error but as pointed
out above, this seems to be deliberate. Thanks for clarifying.
> 
> > 
> > Signed-off-by: Pradeep Goswami <pradeep.goswami@spredtrum.com>
> > Cc: Rebecca Schultz Zavin <rebecca@android.com>
> > Cc: Vladimir Davydov <vdavydov@parallels.com>
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > ---
> > --- a/mm/vmscan.c       2015-11-18 20:55:38.208838142 +0800
> > +++ b/mm/vmscan.c       2015-11-19 14:37:31.189838998 +0800
> > @@ -1806,7 +1806,6 @@ static void shrink_active_list(unsigned
> >  
> >                 if (page_referenced(page, 0, sc->target_mem_cgroup,
> >                                     &vm_flags)) {
> > -                       nr_rotated += hpage_nr_pages(page);
> >                         /*  
> >                          * Identify referenced, file-backed active pages and 
> >                          * give them one more trip around the active list. So
> > @@ -1818,6 +1817,7 @@ static void shrink_active_list(unsigned
> >                          */  
> >                         if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) {
> >                                 list_add(&page->lru, &l_active);
> > +                               nr_rotated += hpage_nr_pages(page);
> >                                 continue;
> >                         }   
> >                 }   
> > 
> > Thanks,
> > Pradeep.
> > --
> > To unsubscribe, send a message with 'unsubscribe linux-mm' in
> > the body to majordomo@kvack.org.  For more info on Linux MM,
> > see: http://www.linux-mm.org/ .
> > Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
> 
> -- 
> Michal Hocko
> SUSE Labs
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