Re: [PATCH] add generic callbacks into compaction

[Gioh Kim <gioh.kim@lge.com>]

2015-04-01 오후 12:46에 Hillf Danton 이(가) 쓴 글:
>>
>> I sent a patch about page allocation for less fragmentation.
>> http://permalink.gmane.org/gmane.linux.kernel.mm/130599
>>
>> It proposes a page allocator allocates pages in the same pageblock
>> for the drivers to move their unmovable pages. Some drivers which comsumes many pages
>> and increases system fragmentation use the allocator to move their pages to
>> decrease fragmentation.
>>
>> I think I can try another approach.
>> There is a compaction code for balloon pages.
>> But the compaction code cannot migrate pages of other drivers.
>> If there is a generic migration framework applicable to any drivers,
>> drivers can register their migration functions.
>> And the compaction can migrate movable pages and also driver's pages.
>>
>> I'm not familiar with virtualization so I couldn't test this patch yet.
>
> A RFC, no?

YES, this is a RFC. It's my fault. I'm sorry.

>> But if mm developers agree with this approach, I will complete this patch.
>>
>> I would do appreciate any feedback.
>>
>> Signed-off-by: Gioh Kim <gioh.kim@lge.com>
>> ---
>>   drivers/virtio/virtio_balloon.c    |    2 ++
>>   include/linux/balloon_compaction.h |   23 +++++++++---
>>   include/linux/fs.h                 |    3 ++
>>   include/linux/pagemap.h            |   26 ++++++++++++++
>>   mm/balloon_compaction.c            |   68 ++++++++++++++++++++++++++++++++++--
>>   mm/compaction.c                    |    7 ++--
>>   mm/migrate.c                       |   24 ++++++-------
>>   7 files changed, 129 insertions(+), 24 deletions(-)
>>
>> diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
>> index 0413157..cd9b8e4 100644
>> --- a/drivers/virtio/virtio_balloon.c
>> +++ b/drivers/virtio/virtio_balloon.c
>> @@ -486,6 +486,8 @@ static int virtballoon_probe(struct virtio_device *vdev)
>>
>>   	balloon_devinfo_init(&vb->vb_dev_info);
>>   #ifdef CONFIG_BALLOON_COMPACTION
>> +	vb->vb_dev_info.mapping = balloon_mapping_alloc(&vb->vb_dev_info,
>> +							&balloon_aops);
>>   	vb->vb_dev_info.migratepage = virtballoon_migratepage;
>>   #endif
>>
>> diff --git a/include/linux/balloon_compaction.h b/include/linux/balloon_compaction.h
>> index 9b0a15d..0af32b3 100644
>> --- a/include/linux/balloon_compaction.h
>> +++ b/include/linux/balloon_compaction.h
>> @@ -62,6 +62,7 @@ struct balloon_dev_info {
>>   	struct list_head pages;		/* Pages enqueued & handled to Host */
>>   	int (*migratepage)(struct balloon_dev_info *, struct page *newpage,
>>   			struct page *page, enum migrate_mode mode);
>> +	struct address_space *mapping;
>
> Better if a comment line is added.

I got it.

>>   };
>>
>>   extern struct page *balloon_page_enqueue(struct balloon_dev_info *b_dev_info);
>> @@ -76,10 +77,22 @@ static inline void balloon_devinfo_init(struct balloon_dev_info *balloon)
>>   }
>>
>>   #ifdef CONFIG_BALLOON_COMPACTION
>> -extern bool balloon_page_isolate(struct page *page);
>> -extern void balloon_page_putback(struct page *page);
>> -extern int balloon_page_migrate(struct page *newpage,
>> -				struct page *page, enum migrate_mode mode);
>> +extern const struct address_space_operations balloon_aops;
>> +extern int balloon_page_isolate(struct page *page);
>> +extern int balloon_page_putback(struct page *page);
>> +extern int balloon_page_migrate(struct address_space *mapping,
>> +				struct page *newpage,
>> +				struct page *page,
>> +				enum migrate_mode mode);
>> +
>> +extern struct address_space
>> +*balloon_mapping_alloc(struct balloon_dev_info *b_dev_info,
>> +		       const struct address_space_operations *a_ops);
>> +
>> +static inline void balloon_mapping_free(struct address_space *balloon_mapping)
>> +{
>> +	kfree(balloon_mapping);
>> +}
>>
>>   /*
>>    * __is_movable_balloon_page - helper to perform @page PageBalloon tests
>> @@ -123,6 +136,7 @@ static inline bool isolated_balloon_page(struct page *page)
>>   static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>>   				       struct page *page)
>>   {
>> +	page->mapping = balloon->mapping;
>>   	__SetPageBalloon(page);
>>   	SetPagePrivate(page);
>>   	set_page_private(page, (unsigned long)balloon);
>> @@ -139,6 +153,7 @@ static inline void balloon_page_insert(struct balloon_dev_info *balloon,
>>    */
>>   static inline void balloon_page_delete(struct page *page)
>>   {
>> +	page->mapping = NULL;
>>   	__ClearPageBalloon(page);
>>   	set_page_private(page, 0);
>>   	if (PagePrivate(page)) {
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index b4d71b5..de463b9 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -368,6 +368,9 @@ struct address_space_operations {
>>   	 */
>>   	int (*migratepage) (struct address_space *,
>>   			struct page *, struct page *, enum migrate_mode);
>> +	int (*isolatepage)(struct page *);
>> +	int (*putbackpage)(struct page *);
>> +
>>   	int (*launder_page) (struct page *);
>>   	int (*is_partially_uptodate) (struct page *, unsigned long,
>>   					unsigned long);
>> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
>> index 4b3736f..715b5b2 100644
>> --- a/include/linux/pagemap.h
>> +++ b/include/linux/pagemap.h
>> @@ -25,6 +25,7 @@ enum mapping_flags {
>>   	AS_MM_ALL_LOCKS	= __GFP_BITS_SHIFT + 2,	/* under mm_take_all_locks() */
>>   	AS_UNEVICTABLE	= __GFP_BITS_SHIFT + 3,	/* e.g., ramdisk, SHM_LOCK */
>>   	AS_EXITING	= __GFP_BITS_SHIFT + 4, /* final truncate in progress */
>> +	AS_MIGRATABLE   = __GFP_BITS_SHIFT + 5,
>>   };
>>
>>   static inline void mapping_set_error(struct address_space *mapping, int error)
>> @@ -54,6 +55,31 @@ static inline int mapping_unevictable(struct address_space *mapping)
>>   	return !!mapping;
>>   }
>>
>> +static inline void mapping_set_migratable(struct address_space *mapping)
>> +{
>> +	set_bit(AS_MIGRATABLE, &mapping->flags);
>> +}
>> +
>> +static inline void mapping_clear_migratable(struct address_space *mapping)
>> +{
>> +	clear_bit(AS_MIGRATABLE, &mapping->flags);
>> +}
>> +
>> +static inline int __mapping_ops(struct address_space *mapping)
>> +{
>> +	return mapping->a_ops &&
>> +		mapping->a_ops->migratepage &&
>> +		mapping->a_ops->isolatepage &&
>> +		mapping->a_ops->putbackpage;
>> +}
>> +
>> +static inline int mapping_migratable(struct address_space *mapping)
>> +{
>> +	if (mapping && __mapping_ops(mapping))
>
> s/__mapping_ops/__mapping_migratable/ given naming hurts brain?

Good. I'll change it. Thank you.

>
>> +		return test_bit(AS_MIGRATABLE, &mapping->flags);
>> +	return !!mapping;
>> +}
>> +
>>   static inline void mapping_set_exiting(struct address_space *mapping)
>>   {
>>   	set_bit(AS_EXITING, &mapping->flags);
>> diff --git a/mm/balloon_compaction.c b/mm/balloon_compaction.c
>> index fcad832..2e9d635 100644
>> --- a/mm/balloon_compaction.c
>> +++ b/mm/balloon_compaction.c
>> @@ -131,8 +131,11 @@ static inline void __putback_balloon_page(struct page *page)
>>   }
>>
>>   /* __isolate_lru_page() counterpart for a ballooned page */
>> -bool balloon_page_isolate(struct page *page)
>> +int balloon_page_isolate(struct page *page)
>>   {
>> +	if (!balloon_page_movable(page))
>> +		return false;
>> +
>>   	/*
>>   	 * Avoid burning cycles with pages that are yet under __free_pages(),
>>   	 * or just got freed under us.
>> @@ -173,8 +176,11 @@ bool balloon_page_isolate(struct page *page)
>>   }
>>
>>   /* putback_lru_page() counterpart for a ballooned page */
>> -void balloon_page_putback(struct page *page)
>> +int balloon_page_putback(struct page *page)
>>   {
>> +	if (!isolated_balloon_page(page))
>> +		return 0;
>> +
>>   	/*
>>   	 * 'lock_page()' stabilizes the page and prevents races against
>>   	 * concurrent isolation threads attempting to re-isolate it.
>> @@ -190,15 +196,20 @@ void balloon_page_putback(struct page *page)
>>   		dump_page(page, "not movable balloon page");
>>   	}
>>   	unlock_page(page);
>> +	return 0;
>>   }
>>
>>   /* move_to_new_page() counterpart for a ballooned page */
>> -int balloon_page_migrate(struct page *newpage,
>> +int balloon_page_migrate(struct address_space *mapping,
>> +			 struct page *newpage,
>
> Looks the newly added mapping is not necessary, yes?

Please refer to struct address_space_operations.
int (*migratepage) (struct address_space *,
		struct page *, struct page *, enum migrate_mode);


>>   			 struct page *page, enum migrate_mode mode)
>>   {
>>   	struct balloon_dev_info *balloon = balloon_page_device(page);
>>   	int rc = -EAGAIN;
>>
>> +	if (!isolated_balloon_page(page))
>> +		return 0;
>> +
>>   	/*
>>   	 * Block others from accessing the 'newpage' when we get around to
>>   	 * establishing additional references. We should be the only one
>> @@ -218,4 +229,55 @@ int balloon_page_migrate(struct page *newpage,
>>   	unlock_page(newpage);
>>   	return rc;
>>   }
>> +
>> +/* define the balloon_mapping->a_ops callback to allow balloon page migration */
>> +const struct address_space_operations balloon_aops = {
>> +	.migratepage = balloon_page_migrate,
>> +	.isolatepage = balloon_page_isolate,
>> +	.putbackpage = balloon_page_putback,
>> +};
>> +EXPORT_SYMBOL_GPL(balloon_aops);
>
>