linux-kernel - Re: [PATCH v4 5/7] add profile information for invalidated page reclaim

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Date:	Wed,  8 Dec 2010 17:02:44 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>,
	linux-mm <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Nick Piggin <npiggin@...nel.dk>, Mel Gorman <mel@....ul.ie>
Subject: Re: [PATCH v4 5/7] add profile information for invalidated page reclaim

> This patch adds profile information about invalidated page reclaim.
> It's just for profiling for test so it would be discard when the series
> are merged.
> 
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> Cc: Rik van Riel <riel@...hat.com>
> Cc: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> Cc: Wu Fengguang <fengguang.wu@...el.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Nick Piggin <npiggin@...nel.dk>
> Cc: Mel Gorman <mel@....ul.ie>
> ---
>  include/linux/vmstat.h |    4 ++--
>  mm/swap.c              |    3 +++
>  mm/vmstat.c            |    3 +++
>  3 files changed, 8 insertions(+), 2 deletions(-)

Today, we have tracepoint. tracepoint has no overhead if it's unused.
but vmstat has a overhead even if unused.

Then, all new vmstat proposal should be described why you think it is
frequently used from administrators.




> 
> diff --git a/include/linux/vmstat.h b/include/linux/vmstat.h
> index 833e676..c38ad95 100644
> --- a/include/linux/vmstat.h
> +++ b/include/linux/vmstat.h
> @@ -30,8 +30,8 @@
>  
>  enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>  		FOR_ALL_ZONES(PGALLOC),
> -		PGFREE, PGACTIVATE, PGDEACTIVATE,
> -		PGFAULT, PGMAJFAULT,
> +		PGFREE, PGACTIVATE, PGDEACTIVATE, PGINVALIDATE,
> +		PGRECLAIM, PGFAULT, PGMAJFAULT,
>  		FOR_ALL_ZONES(PGREFILL),
>  		FOR_ALL_ZONES(PGSTEAL),
>  		FOR_ALL_ZONES(PGSCAN_KSWAPD),
> diff --git a/mm/swap.c b/mm/swap.c
> index 0f23998..2f21e6e 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -317,6 +317,7 @@ static void lru_deactivate(struct page *page, struct zone *zone)
>  		 * is _really_ small and  it's non-critical problem.
>  		 */
>  		SetPageReclaim(page);
> +		__count_vm_event(PGRECLAIM);

Um. No.
This is not reclaim operation anyway. Userland folks shouldn't know
you override PG_reclaim. It's implementaion internal information.



>  	} else {
>  		/*
>  		 * The page's writeback ends up during pagevec
> @@ -328,6 +329,8 @@ static void lru_deactivate(struct page *page, struct zone *zone)
>  
>  	if (active)
>  		__count_vm_event(PGDEACTIVATE);
> +
> +	__count_vm_event(PGINVALIDATE);
>  	update_page_reclaim_stat(zone, page, file, 0);

I have similar complains as above.
If you use PGINVALIDATE, other invalidate pass should update this counter too.


>  }
>  
> diff --git a/mm/vmstat.c b/mm/vmstat.c
> index 3555636..ef6102d 100644
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -818,6 +818,9 @@ static const char * const vmstat_text[] = {
>  	"pgactivate",
>  	"pgdeactivate",
>  
> +	"pginvalidate",
> +	"pgreclaim",
> +
>  	"pgfault",
>  	"pgmajfault",
>  
> -- 
> 1.7.0.4
> 



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