Re: [PATCH v3 15/21] mm: handle lruvec relocks on lumpy reclaim

[Konstantin Khlebnikov <khlebnikov@openvz.org>]

KAMEZAWA Hiroyuki wrote:
> On Thu, 23 Feb 2012 17:52:52 +0400
> Konstantin Khlebnikov<khlebnikov@openvz.org>  wrote:
>
>> Prepare for lock splitting in lumly reclaim logic.
>> Now move_active_pages_to_lru() and putback_inactive_pages()
>> can put pages into different lruvecs.
>>
>> * relock book before SetPageLRU()
>
> lruvec ?

yeah, this came from v1

>
>> * update reclaim_stat pointer after relocks
>> * return currently locked lruvec
>>
>> Signed-off-by: Konstantin Khlebnikov<khlebnikov@openvz.org>
>> ---
>>   mm/vmscan.c |   45 +++++++++++++++++++++++++++++++++------------
>>   1 files changed, 33 insertions(+), 12 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index a3941d1..6eeeb4b 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1114,6 +1114,7 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>>   		unsigned long *nr_scanned, struct scan_control *sc,
>>   		isolate_mode_t mode, int active, int file)
>>   {
>> +	struct lruvec *cursor_lruvec = lruvec;
>>   	struct list_head *src;
>>   	unsigned long nr_taken = 0;
>>   	unsigned long nr_lumpy_taken = 0;
>> @@ -1197,14 +1198,17 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>>   			    !PageSwapCache(cursor_page))
>>   				break;
>>
>> +			/* Switch cursor_lruvec lock for lumpy isolate */
>> +			if (!__lock_page_lruvec_irq(&cursor_lruvec,
>> +						    cursor_page))
>> +				continue;
>> +
>>   			if (__isolate_lru_page(cursor_page, mode, file) == 0) {
>>   				unsigned int isolated_pages;
>> -				struct lruvec *cursor_lruvec;
>>   				int cursor_lru = page_lru(cursor_page);
>>
>>   				list_move(&cursor_page->lru, dst);
>>   				isolated_pages = hpage_nr_pages(cursor_page);
>> -				cursor_lruvec = page_lruvec(cursor_page);
>>   				cursor_lruvec->pages_count[cursor_lru] -=
>>   								isolated_pages;
>>   				VM_BUG_ON((long)cursor_lruvec->
>> @@ -1235,6 +1239,9 @@ static unsigned long isolate_lru_pages(unsigned long nr_to_scan,
>>   			}
>>   		}
>>
>> +		/* Restore original lruvec lock */
>> +		cursor_lruvec = __relock_page_lruvec(cursor_lruvec, page);
>> +
>>   		/* If we break out of the loop above, lumpy reclaim failed */
>>   		if (pfn<  end_pfn)
>>   			nr_lumpy_failed++;
>> @@ -1325,7 +1332,10 @@ static int too_many_isolated(struct zone *zone, int file,
>>   	return isolated>  inactive;
>>   }
>>
>> -static noinline_for_stack void
>> +/*
>> + * Returns currently locked lruvec
>> + */
>> +static noinline_for_stack struct lruvec *
>>   putback_inactive_pages(struct lruvec *lruvec,
>>   		       struct list_head *page_list)
>>   {
>> @@ -1347,10 +1357,13 @@ putback_inactive_pages(struct lruvec *lruvec,
>>   			lock_lruvec_irq(lruvec);
>>   			continue;
>>   		}
>> +
>> +		lruvec = __relock_page_lruvec(lruvec, page);
>> +		reclaim_stat =&lruvec->reclaim_stat;
>> +
>>   		SetPageLRU(page);
>>   		lru = page_lru(page);
>>
>> -		lruvec = page_lruvec(page);
>>   		add_page_to_lru_list(lruvec, page, lru);
>>   		if (is_active_lru(lru)) {
>>   			int file = is_file_lru(lru);
>> @@ -1375,6 +1388,8 @@ putback_inactive_pages(struct lruvec *lruvec,
>>   	 * To save our caller's stack, now use input list for pages to free.
>>   	 */
>>   	list_splice(&pages_to_free, page_list);
>> +
>> +	return lruvec;
>>   }
>>
>>   static noinline_for_stack void
>> @@ -1544,7 +1559,7 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
>>   		__count_vm_events(KSWAPD_STEAL, nr_reclaimed);
>>   	__count_zone_vm_events(PGSTEAL, zone, nr_reclaimed);
>>
>> -	putback_inactive_pages(lruvec,&page_list);
>> +	lruvec = putback_inactive_pages(lruvec,&page_list);
>>
>>   	__mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon);
>>   	__mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file);
>> @@ -1603,12 +1618,15 @@ shrink_inactive_list(unsigned long nr_to_scan, struct lruvec *lruvec,
>>    *
>>    * The downside is that we have to touch page->_count against each page.
>>    * But we had to alter page->flags anyway.
>> + *
>> + * Returns currently locked lruvec
>>    */
>>
>> -static void move_active_pages_to_lru(struct lruvec *lruvec,
>> -				     struct list_head *list,
>> -				     struct list_head *pages_to_free,
>> -				     enum lru_list lru)
>> +static struct lruvec *
>> +move_active_pages_to_lru(struct lruvec *lruvec,
>> +			 struct list_head *list,
>> +			 struct list_head *pages_to_free,
>> +			 enum lru_list lru)
>>   {
>>   	unsigned long pgmoved = 0;
>>   	struct page *page;
>> @@ -1630,10 +1648,11 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
>>
>>   		page = lru_to_page(list);
>>
>> +		lruvec = __relock_page_lruvec(lruvec, page);
>> +
>>   		VM_BUG_ON(PageLRU(page));
>>   		SetPageLRU(page);
>>
>> -		lruvec = page_lruvec(page);
>>   		list_move(&page->lru,&lruvec->pages_lru[lru]);
>>   		numpages = hpage_nr_pages(page);
>>   		lruvec->pages_count[lru] += numpages;
>> @@ -1655,6 +1674,8 @@ static void move_active_pages_to_lru(struct lruvec *lruvec,
>>   	__mod_zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru, pgmoved);
>>   	if (!is_active_lru(lru))
>>   		__count_vm_events(PGDEACTIVATE, pgmoved);
>> +
>> +	return lruvec;
>>   }
>>
>>   static void shrink_active_list(unsigned long nr_to_scan,
>> @@ -1744,9 +1765,9 @@ static void shrink_active_list(unsigned long nr_to_scan,
>>   	 */
>>   	reclaim_stat->recent_rotated[file] += nr_rotated;
>>
>> -	move_active_pages_to_lru(lruvec,&l_active,&l_hold,
>> +	lruvec = move_active_pages_to_lru(lruvec,&l_active,&l_hold,
>>   						LRU_ACTIVE + file * LRU_FILE);
>> -	move_active_pages_to_lru(lruvec,&l_inactive,&l_hold,
>> +	lruvec = move_active_pages_to_lru(lruvec,&l_inactive,&l_hold,
>>   						LRU_BASE   + file * LRU_FILE);
>>   	__mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken);
>>   	unlock_lruvec_irq(lruvec);
>>
>
> Hmm...could you add comments to each function as
> "The caller should _lock_ lruvec before calling this functions.
>   This function returns a lruvec with _locked_. It may be different from passed one.
>   And The callser should unlock lruvec"

Ok. Documenting is not my best side =)

>
>
> Thanks,
> -Kame
>
>
>
>
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