linux-kernel - Re: [PATCH 18/25] Do not disable interrupts in free_page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20090422091144.626B.A69D9226@jp.fujitsu.com>
Date:	Wed, 22 Apr 2009 09:13:10 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	kosaki.motohiro@...fujitsu.com,
	Linux Memory Management List <linux-mm@...ck.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Nick Piggin <npiggin@...e.de>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Zhang Yanmin <yanmin_zhang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Lee Schermerhorn <Lee.Schermerhorn@...com>
Subject: Re: [PATCH 18/25] Do not disable interrupts in free_page_mlock()

(cc to Lee)

> free_page_mlock() tests and clears PG_mlocked using locked versions of the
> bit operations. If set, it disables interrupts to update counters and this
> happens on every page free even though interrupts are disabled very shortly
> afterwards a second time.  This is wasteful.
> 
> This patch splits what free_page_mlock() does. The bit check is still
> made. However, the update of counters is delayed until the interrupts are
> disabled and the non-lock version for clearing the bit is used. One potential
> weirdness with this split is that the counters do not get updated if the
> bad_page() check is triggered but a system showing bad pages is getting
> screwed already.

Looks good. thanks good improvement.
I hope Lee also ack this.

	Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>


  -kosaki


> 
> Signed-off-by: Mel Gorman <mel@....ul.ie>
> Reviewed-by: Christoph Lameter <cl@...ux-foundation.org>
> ---
>  mm/internal.h   |   11 +++--------
>  mm/page_alloc.c |    8 +++++++-
>  2 files changed, 10 insertions(+), 9 deletions(-)
> 
> diff --git a/mm/internal.h b/mm/internal.h
> index 987bb03..58ec1bc 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -157,14 +157,9 @@ static inline void mlock_migrate_page(struct page *newpage, struct page *page)
>   */
>  static inline void free_page_mlock(struct page *page)
>  {
> -	if (unlikely(TestClearPageMlocked(page))) {
> -		unsigned long flags;
> -
> -		local_irq_save(flags);
> -		__dec_zone_page_state(page, NR_MLOCK);
> -		__count_vm_event(UNEVICTABLE_MLOCKFREED);
> -		local_irq_restore(flags);
> -	}
> +	__ClearPageMlocked(page);
> +	__dec_zone_page_state(page, NR_MLOCK);
> +	__count_vm_event(UNEVICTABLE_MLOCKFREED);
>  }
>  
>  #else /* CONFIG_HAVE_MLOCKED_PAGE_BIT */
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index a1ca038..bf4b8d9 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -499,7 +499,6 @@ static inline void __free_one_page(struct page *page,
>  
>  static inline int free_pages_check(struct page *page)
>  {
> -	free_page_mlock(page);
>  	if (unlikely(page_mapcount(page) |
>  		(page->mapping != NULL)  |
>  		(page_count(page) != 0)  |
> @@ -556,6 +555,7 @@ static void __free_pages_ok(struct page *page, unsigned int order)
>  	unsigned long flags;
>  	int i;
>  	int bad = 0;
> +	int clearMlocked = PageMlocked(page);
>  
>  	for (i = 0 ; i < (1 << order) ; ++i)
>  		bad += free_pages_check(page + i);
> @@ -571,6 +571,8 @@ static void __free_pages_ok(struct page *page, unsigned int order)
>  	kernel_map_pages(page, 1 << order, 0);
>  
>  	local_irq_save(flags);
> +	if (unlikely(clearMlocked))
> +		free_page_mlock(page);
>  	__count_vm_events(PGFREE, 1 << order);
>  	free_one_page(page_zone(page), page, order,
>  					get_pageblock_migratetype(page));
> @@ -1018,6 +1020,7 @@ static void free_hot_cold_page(struct page *page, int cold)
>  	struct zone *zone = page_zone(page);
>  	struct per_cpu_pages *pcp;
>  	unsigned long flags;
> +	int clearMlocked = PageMlocked(page);
>  
>  	if (PageAnon(page))
>  		page->mapping = NULL;
> @@ -1033,7 +1036,10 @@ static void free_hot_cold_page(struct page *page, int cold)
>  
>  	pcp = &zone_pcp(zone, get_cpu())->pcp;
>  	local_irq_save(flags);
> +	if (unlikely(clearMlocked))
> +		free_page_mlock(page);
>  	__count_vm_event(PGFREE);
> +
>  	if (cold)
>  		list_add_tail(&page->lru, &pcp->list);
>  	else
> -- 
> 1.5.6.5
> 



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/