Re: [PATCH 2/3] Reclaim invalidated page ASAP

[Mel Gorman]

On Tue, Nov 30, 2010 at 07:41:30AM +0900, Minchan Kim wrote:
> On Mon, Nov 29, 2010 at 04:57:06PM +0000, Mel Gorman wrote:
> > On Tue, Nov 30, 2010 at 12:23:20AM +0900, Minchan Kim wrote:
> > > invalidate_mapping_pages is very big hint to reclaimer.
> > > It means user doesn't want to use the page any more.
> > > So in order to prevent working set page eviction, this patch
> > > move the page into tail of inactive list by PG_reclaim.
> > > 
> > > Please, remember that pages in inactive list are working set
> > > as well as active list. If we don't move pages into inactive list's
> > > tail, pages near by tail of inactive list can be evicted although
> > > we have a big clue about useless pages. It's totally bad.
> > > 
> > > Now PG_readahead/PG_reclaim is shared.
> > > fe3cba17 added ClearPageReclaim into clear_page_dirty_for_io for
> > > preventing fast reclaiming readahead marker page.
> > > 
> > > In this series, PG_reclaim is used by invalidated page, too.
> > > If VM find the page is invalidated and it's dirty, it sets PG_reclaim
> > > to reclaim asap. Then, when the dirty page will be writeback,
> > > clear_page_dirty_for_io will clear PG_reclaim unconditionally.
> > > It disturbs this serie's goal.
> > > 
> > > I think it's okay to clear PG_readahead when the page is dirty, not
> > > writeback time. So this patch moves ClearPageReadahead.
> > > 
> > > Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> > > Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> > > Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> > > Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> > > Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> > > Cc: Nick Piggin <npiggin@xxxxxxxxx>
> > > Cc: Mel Gorman <mel@xxxxxxxxx>
> > > 
> > > Changelog since v2:
> > >  - put ClearPageReclaim in set_page_dirty - suggested by Wu.
> > >  
> > > Changelog since v1:
> > >  - make the invalidated page reclaim asap - suggested by Andrew.
> > > ---
> > >  mm/page-writeback.c |   12 +++++++++++-
> > >  mm/swap.c           |   48 +++++++++++++++++++++++++++++++++++-------------
> > >  2 files changed, 46 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> > > index fc93802..88587a5 100644
> > > --- a/mm/page-writeback.c
> > > +++ b/mm/page-writeback.c
> > > @@ -1250,6 +1250,17 @@ int set_page_dirty(struct page *page)
> > >  {
> > >  	struct address_space *mapping = page_mapping(page);
> > >  
> > > +	/*
> > > +	 * readahead/lru_deactivate_page could remain
> > > +	 * PG_readahead/PG_reclaim due to race with end_page_writeback
> > > +	 * About readahead, if the page is written, the flags would be
> > > +	 * reset. So no problem.
> > > +	 * About lru_deactivate_page, if the page is redirty, the flag
> > > +	 * will be reset. So no problem. but if the page is used by readahead
> > > +	 * it will confuse readahead and  make it restart the size rampup
> > > +	 * process. But it's a trivial problem.
> > > +	 */
> > > +	ClearPageReclaim(page);
> > >  	if (likely(mapping)) {
> > >  		int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
> > >  #ifdef CONFIG_BLOCK
> > > @@ -1307,7 +1318,6 @@ int clear_page_dirty_for_io(struct page *page)
> > >  
> > >  	BUG_ON(!PageLocked(page));
> > >  
> > > -	ClearPageReclaim(page);
> > >  	if (mapping && mapping_cap_account_dirty(mapping)) {
> > >  		/*
> > >  		 * Yes, Virginia, this is indeed insane.
> > > diff --git a/mm/swap.c b/mm/swap.c
> > > index 19e0812..936b281 100644
> > > --- a/mm/swap.c
> > > +++ b/mm/swap.c
> > > @@ -275,28 +275,50 @@ void add_page_to_unevictable_list(struct page *page)
> > >   * into inative list's head. Because the VM expects the page would
> > >   * be writeout by flusher. The flusher's writeout is much effective
> > >   * than reclaimer's random writeout.
> > > + *
> > > + * If the page isn't page_mapped and dirty/writeback, the page
> > > + * could reclaim asap using PG_reclaim.
> > > + *
> > > + * 1. active, mapped page -> none
> > > + * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
> > > + * 3. inactive, mapped page -> none
> > > + * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
> > > + * 5. Others -> none
> > > + *
> > > + * In 4, why it moves inactive's head, the VM expects the page would
> > > + * be writeout by flusher. The flusher's writeout is much effective than
> > > + * reclaimer's random writeout.
> > >   */
> > >  static void __lru_deactivate(struct page *page, struct zone *zone)
> > >  {
> > >  	int lru, file;
> > > -	unsigned long vm_flags;
> > > +	int active = 0;
> > >  
> > > -	if (!PageLRU(page) || !PageActive(page))
> > > +	if (!PageLRU(page))
> > >  		return;
> > > -
> > >  	/* Some processes are using the page */
> > >  	if (page_mapped(page))
> > >  		return;
> > > -
> > > -	file = page_is_file_cache(page);
> > > -	lru = page_lru_base_type(page);
> > > -	del_page_from_lru_list(zone, page, lru + LRU_ACTIVE);
> > > -	ClearPageActive(page);
> > > -	ClearPageReferenced(page);
> > > -	add_page_to_lru_list(zone, page, lru);
> > > -	__count_vm_event(PGDEACTIVATE);
> > > -
> > > -	update_page_reclaim_stat(zone, page, file, 0);
> > > +	if (PageActive(page))
> > > +		active = 1;
> > > +
> > > +	if (PageWriteback(page) || PageDirty(page)) {
> > > +		/*
> > > +		 * PG_reclaim could be raced with end_page_writeback
> > > +		 * It can make readahead confusing.  But race window
> > > +		 * is _really_ small and  it's non-critical problem.
> > > +		 */
> > > +		SetPageReclaim(page);
> > > +
> > > +		file = page_is_file_cache(page);
> > > +		lru = page_lru_base_type(page);
> > > +		del_page_from_lru_list(zone, page, lru + active);
> > > +		ClearPageActive(page);
> > > +		ClearPageReferenced(page);
> > > +		add_page_to_lru_list(zone, page, lru);
> > > +		__count_vm_event(PGDEACTIVATE);
> > 
> > You update PGDEACTIVATE whether the page was active or not.
> 
> My fault. 
> Resend.
> 
> Subject: [PATCH v3 2/3] Reclaim invalidated page ASAP
> 
> invalidate_mapping_pages is very big hint to reclaimer.
> It means user doesn't want to use the page any more.
> So in order to prevent working set page eviction, this patch
> move the page into tail of inactive list by PG_reclaim.
> 
> Please, remember that pages in inactive list are working set
> as well as active list. If we don't move pages into inactive list's
> tail, pages near by tail of inactive list can be evicted although
> we have a big clue about useless pages. It's totally bad.
> 
> Now PG_readahead/PG_reclaim is shared.
> fe3cba17 added ClearPageReclaim into clear_page_dirty_for_io for
> preventing fast reclaiming readahead marker page.
> 
> In this series, PG_reclaim is used by invalidated page, too.
> If VM find the page is invalidated and it's dirty, it sets PG_reclaim
> to reclaim asap. Then, when the dirty page will be writeback,
> clear_page_dirty_for_io will clear PG_reclaim unconditionally.
> It disturbs this serie's goal.
> 
> I think it's okay to clear PG_readahead when the page is dirty, not
> writeback time. So this patch moves ClearPageReadahead.
> 
> Signed-off-by: Minchan Kim <minchan.kim@xxxxxxxxx>
> Acked-by: Rik van Riel <riel@xxxxxxxxxx>
> Cc: Wu Fengguang <fengguang.wu@xxxxxxxxx>
> Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
> Cc: Nick Piggin <npiggin@xxxxxxxxx>
> Cc: Mel Gorman <mel@xxxxxxxxx>
> 
> Changelog since v2:
>  - put ClearPageReclaim in set_page_dirty - suggested by Wu.
> 
> Changelog since v1:
>  - make the invalidated page reclaim asap - suggested by Andrew.
> ---
>  mm/page-writeback.c |   12 +++++++++++-
>  mm/swap.c           |   49 ++++++++++++++++++++++++++++++++++++-------------
>  2 files changed, 47 insertions(+), 14 deletions(-)
> 
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index fc93802..88587a5 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1250,6 +1250,17 @@ int set_page_dirty(struct page *page)
>  {
>  	struct address_space *mapping = page_mapping(page);
>  
> +	/*
> +	 * readahead/lru_deactivate_page could remain
> +	 * PG_readahead/PG_reclaim due to race with end_page_writeback
> +	 * About readahead, if the page is written, the flags would be
> +	 * reset. So no problem.
> +	 * About lru_deactivate_page, if the page is redirty, the flag
> +	 * will be reset. So no problem. but if the page is used by readahead
> +	 * it will confuse readahead and  make it restart the size rampup
> +	 * process. But it's a trivial problem.
> +	 */
> +	ClearPageReclaim(page);
>  	if (likely(mapping)) {
>  		int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
>  #ifdef CONFIG_BLOCK
> @@ -1307,7 +1318,6 @@ int clear_page_dirty_for_io(struct page *page)
>  
>  	BUG_ON(!PageLocked(page));
>  
> -	ClearPageReclaim(page);
>  	if (mapping && mapping_cap_account_dirty(mapping)) {
>  		/*
>  		 * Yes, Virginia, this is indeed insane.
> diff --git a/mm/swap.c b/mm/swap.c
> index 19e0812..1f1f435 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -275,28 +275,51 @@ void add_page_to_unevictable_list(struct page *page)
>   * into inative list's head. Because the VM expects the page would
>   * be writeout by flusher. The flusher's writeout is much effective
>   * than reclaimer's random writeout.
> + *
> + * If the page isn't page_mapped and dirty/writeback, the page
> + * could reclaim asap using PG_reclaim.
> + *
> + * 1. active, mapped page -> none
> + * 2. active, dirty/writeback page -> inactive, head, PG_reclaim
> + * 3. inactive, mapped page -> none
> + * 4. inactive, dirty/writeback page -> inactive, head, PG_reclaim
> + * 5. Others -> none
> + *
> + * In 4, why it moves inactive's head, the VM expects the page would
> + * be writeout by flusher. The flusher's writeout is much effective than
> + * reclaimer's random writeout.
>   */
>  static void __lru_deactivate(struct page *page, struct zone *zone)
>  {
>  	int lru, file;
> -	unsigned long vm_flags;
> +	int active = 0;
>  
> -	if (!PageLRU(page) || !PageActive(page))
> +	if (!PageLRU(page))
>  		return;
> -
>  	/* Some processes are using the page */
>  	if (page_mapped(page))
>  		return;
> -
> -	file = page_is_file_cache(page);
> -	lru = page_lru_base_type(page);
> -	del_page_from_lru_list(zone, page, lru + LRU_ACTIVE);
> -	ClearPageActive(page);
> -	ClearPageReferenced(page);
> -	add_page_to_lru_list(zone, page, lru);
> -	__count_vm_event(PGDEACTIVATE);
> -
> -	update_page_reclaim_stat(zone, page, file, 0);
> +	if (PageActive(page))
> +		active = 1;
> +

I should have said this the last time but if you do another revision,
make active a "bool". There is a very slow migration of int to bool in
cases it makes sense. It's not urgent though.

> +	if (PageWriteback(page) || PageDirty(page)) {
> +		/*
> +		 * PG_reclaim could be raced with end_page_writeback
> +		 * It can make readahead confusing.  But race window
> +		 * is _really_ small and  it's non-critical problem.
> +		 */
> +		SetPageReclaim(page);
> +
> +		file = page_is_file_cache(page);
> +		lru = page_lru_base_type(page);
> +		del_page_from_lru_list(zone, page, lru + active);
> +		ClearPageActive(page);
> +		ClearPageReferenced(page);
> +		add_page_to_lru_list(zone, page, lru);
> +		if (active)
> +			__count_vm_event(PGDEACTIVATE);
> +		update_page_reclaim_stat(zone, page, file, 0);
> +	}
>  }
>  

Whether you update active's type or not;

Acked-by: Mel Gorman <mel@xxxxxxxxx>

-- 
Mel Gorman
Part-time Phd Student                          Linux Technology Center
University of Limerick                         IBM Dublin Software Lab
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