Re: [PATCH 3/7] mm: rework __isolate_lru_page() file/anon filter

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 02 Mar 2012 09:51:27 +0400
Konstantin Khlebnikov <khlebnikov@openvz.org> wrote:

> KAMEZAWA Hiroyuki wrote:
> > On Wed, 29 Feb 2012 13:15:47 +0400
> > Konstantin Khlebnikov<khlebnikov@openvz.org>  wrote:
> >
> >> This patch adds file/anon filter bits into isolate_mode_t,
> >> this allows to simplify checks in __isolate_lru_page().
> >>
> >> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
> >
> > Hmm.. I like idea but..
> >
> >> ---
> >>   include/linux/mmzone.h |    4 ++++
> >>   include/linux/swap.h   |    2 +-
> >>   mm/compaction.c        |    5 +++--
> >>   mm/vmscan.c            |   27 +++++++++++++--------------
> >>   4 files changed, 21 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
> >> index eff4918..2fed935 100644
> >> --- a/include/linux/mmzone.h
> >> +++ b/include/linux/mmzone.h
> >> @@ -193,6 +193,10 @@ struct lruvec {
> >>   #define ISOLATE_UNMAPPED	((__force isolate_mode_t)0x8)
> >>   /* Isolate for asynchronous migration */
> >>   #define ISOLATE_ASYNC_MIGRATE	((__force isolate_mode_t)0x10)
> >> +/* Isolate swap-backed pages */
> >> +#define	ISOLATE_ANON		((__force isolate_mode_t)0x20)
> >> +/* Isolate file-backed pages */
> >> +#define	ISOLATE_FILE		((__force isolate_mode_t)0x40)
> >>
> >>   /* LRU Isolation modes. */
> >>   typedef unsigned __bitwise__ isolate_mode_t;
> >> diff --git a/include/linux/swap.h b/include/linux/swap.h
> >> index ba2c8d7..dc6e6a3 100644
> >> --- a/include/linux/swap.h
> >> +++ b/include/linux/swap.h
> >> @@ -254,7 +254,7 @@ static inline void lru_cache_add_file(struct page *page)
> >>   /* linux/mm/vmscan.c */
> >>   extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
> >>   					gfp_t gfp_mask, nodemask_t *mask);
> >> -extern int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file);
> >> +extern int __isolate_lru_page(struct page *page, isolate_mode_t mode);
> >>   extern unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem,
> >>   						  gfp_t gfp_mask, bool noswap);
> >>   extern unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem,
> >> diff --git a/mm/compaction.c b/mm/compaction.c
> >> index 74a8c82..cc054f7 100644
> >> --- a/mm/compaction.c
> >> +++ b/mm/compaction.c
> >> @@ -261,7 +261,8 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
> >>   	unsigned long last_pageblock_nr = 0, pageblock_nr;
> >>   	unsigned long nr_scanned = 0, nr_isolated = 0;
> >>   	struct list_head *migratelist =&cc->migratepages;
> >> -	isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE;
> >> +	isolate_mode_t mode = ISOLATE_ACTIVE | ISOLATE_INACTIVE |
> >> +			      ISOLATE_FILE | ISOLATE_ANON;
> >>
> >>   	/* Do not scan outside zone boundaries */
> >>   	low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
> >> @@ -375,7 +376,7 @@ static isolate_migrate_t isolate_migratepages(struct zone *zone,
> >>   			mode |= ISOLATE_ASYNC_MIGRATE;
> >>
> >>   		/* Try isolate the page */
> >> -		if (__isolate_lru_page(page, mode, 0) != 0)
> >> +		if (__isolate_lru_page(page, mode) != 0)
> >>   			continue;
> >>
> >>   		VM_BUG_ON(PageTransCompound(page));
> >> diff --git a/mm/vmscan.c b/mm/vmscan.c
> >> index af6cfe7..1b70338 100644
> >> --- a/mm/vmscan.c
> >> +++ b/mm/vmscan.c
> >> @@ -1029,27 +1029,18 @@ keep_lumpy:
> >>    *
> >>    * returns 0 on success, -ve errno on failure.
> >>    */
> >> -int __isolate_lru_page(struct page *page, isolate_mode_t mode, int file)
> >> +int __isolate_lru_page(struct page *page, isolate_mode_t mode)
> >>   {
> >> -	bool all_lru_mode;
> >>   	int ret = -EINVAL;
> >>
> >>   	/* Only take pages on the LRU. */
> >>   	if (!PageLRU(page))
> >>   		return ret;
> >>
> >> -	all_lru_mode = (mode&  (ISOLATE_ACTIVE|ISOLATE_INACTIVE)) ==
> >> -		(ISOLATE_ACTIVE|ISOLATE_INACTIVE);
> >> -
> >> -	/*
> >> -	 * When checking the active state, we need to be sure we are
> >> -	 * dealing with comparible boolean values.  Take the logical not
> >> -	 * of each.
> >> -	 */
> >> -	if (!all_lru_mode&&  !PageActive(page) != !(mode&  ISOLATE_ACTIVE))
> >> +	if (!(mode&  (PageActive(page) ? ISOLATE_ACTIVE : ISOLATE_INACTIVE)))
> >>   		return ret;
> >
> > Isn't this complicated ?
> 
> But it doesn't blows my mind as old code does =)
> 
> Maybe someone can propose more clear variant?
> 

switch (mode & (ISOLATE_ACTIVE | ISOLATE_INACTIVE)) {
	case ISOLATE_ACTIVE :
		if (!PageActive(page))
			return ret;
	case ISOLATE_INACTIVE :
		if (PageActive(page))
			return ret;
	default:
		break;
	}
}

?

Thanks,
-Kame

> >
> >>
> >> -	if (!all_lru_mode&&  !!page_is_file_cache(page) != file)
> >> +	if (!(mode&  (page_is_file_cache(page) ? ISOLATE_FILE : ISOLATE_ANON)))
> >>   		return ret;
> >>
> >>   	/*
> >
> > ditto.
> >
> > Where is simple  ?
> >
> > Thanks,
> > -Kame
> >
> 
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