* [PATCH] mm: reset migratetype if the range spans two pageblocks
@ 2015-10-16 10:06 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2015-10-16 10:06 UTC (permalink / raw)
To: Andrew Morton, Vlastimil Babka, Mel Gorman, mhocko, js1304,
Johannes Weiner, alexander.h.duyck, zhongjiang
Cc: Linux MM, LKML
__rmqueue_fallback() will change the migratetype of pageblock,
so it is possible that two continuous pageblocks have different
migratetypes.
When freeing all pages of the two blocks, they will be merged
to 4M, and added to the buddy list which the migratetype is the
first pageblock's.
If later alloc some pages and split the 4M, the second pageblock
will be added to the buddy list, and the migratetype is the first
pageblock's, so it is different from the its pageblock's.
That means the page in buddy list's migratetype is different from
the page in pageblock's migratetype. This will make confusion.
However,if we change the hotpath, it will be performance degradation,
so any better ideas?
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
---
mm/page_alloc.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 48aaf7b..5c91348 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
out:
zone->free_area[order].nr_free++;
+ /* If the range spans two pageblocks, reset the migratetype. */
+ if (order > pageblock_order)
+ change_pageblock_range(page, order, migratetype);
}
static inline int free_pages_check(struct page *page)
--
2.0.0
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH] mm: reset migratetype if the range spans two pageblocks
@ 2015-10-16 10:06 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2015-10-16 10:06 UTC (permalink / raw)
To: Andrew Morton, Vlastimil Babka, Mel Gorman, mhocko, js1304,
Johannes Weiner, alexander.h.duyck, zhongjiang
Cc: Linux MM, LKML
__rmqueue_fallback() will change the migratetype of pageblock,
so it is possible that two continuous pageblocks have different
migratetypes.
When freeing all pages of the two blocks, they will be merged
to 4M, and added to the buddy list which the migratetype is the
first pageblock's.
If later alloc some pages and split the 4M, the second pageblock
will be added to the buddy list, and the migratetype is the first
pageblock's, so it is different from the its pageblock's.
That means the page in buddy list's migratetype is different from
the page in pageblock's migratetype. This will make confusion.
However,if we change the hotpath, it will be performance degradation,
so any better ideas?
Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
---
mm/page_alloc.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 48aaf7b..5c91348 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
out:
zone->free_area[order].nr_free++;
+ /* If the range spans two pageblocks, reset the migratetype. */
+ if (order > pageblock_order)
+ change_pageblock_range(page, order, migratetype);
}
static inline int free_pages_check(struct page *page)
--
2.0.0
--
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^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] mm: reset migratetype if the range spans two pageblocks
2015-10-16 10:06 ` Xishi Qiu
@ 2015-10-16 10:12 ` Xishi Qiu
-1 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2015-10-16 10:12 UTC (permalink / raw)
To: Andrew Morton, Vlastimil Babka, Mel Gorman, mhocko, js1304,
Johannes Weiner, alexander.h.duyck, zhongjiang
Cc: Linux MM, LKML
On 2015/10/16 18:06, Xishi Qiu wrote:
> __rmqueue_fallback() will change the migratetype of pageblock,
> so it is possible that two continuous pageblocks have different
> migratetypes.
>
> When freeing all pages of the two blocks, they will be merged
> to 4M, and added to the buddy list which the migratetype is the
> first pageblock's.
>
> If later alloc some pages and split the 4M, the second pageblock
> will be added to the buddy list, and the migratetype is the first
> pageblock's, so it is different from the its pageblock's.
>
> That means the page in buddy list's migratetype is different from
> the page in pageblock's migratetype. This will make confusion.
>
> However,if we change the hotpath, it will be performance degradation,
> so any better ideas?
>
How about using get_pfnblock_migratetype() to get the pageblock's
migratetype first, and compare them?
Thanks,
Xishi Qiu
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 48aaf7b..5c91348 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
> list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
> out:
> zone->free_area[order].nr_free++;
> + /* If the range spans two pageblocks, reset the migratetype. */
> + if (order > pageblock_order)
> + change_pageblock_range(page, order, migratetype);
> }
>
> static inline int free_pages_check(struct page *page)
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm: reset migratetype if the range spans two pageblocks
@ 2015-10-16 10:12 ` Xishi Qiu
0 siblings, 0 replies; 7+ messages in thread
From: Xishi Qiu @ 2015-10-16 10:12 UTC (permalink / raw)
To: Andrew Morton, Vlastimil Babka, Mel Gorman, mhocko, js1304,
Johannes Weiner, alexander.h.duyck, zhongjiang
Cc: Linux MM, LKML
On 2015/10/16 18:06, Xishi Qiu wrote:
> __rmqueue_fallback() will change the migratetype of pageblock,
> so it is possible that two continuous pageblocks have different
> migratetypes.
>
> When freeing all pages of the two blocks, they will be merged
> to 4M, and added to the buddy list which the migratetype is the
> first pageblock's.
>
> If later alloc some pages and split the 4M, the second pageblock
> will be added to the buddy list, and the migratetype is the first
> pageblock's, so it is different from the its pageblock's.
>
> That means the page in buddy list's migratetype is different from
> the page in pageblock's migratetype. This will make confusion.
>
> However,if we change the hotpath, it will be performance degradation,
> so any better ideas?
>
How about using get_pfnblock_migratetype() to get the pageblock's
migratetype first, and compare them?
Thanks,
Xishi Qiu
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 48aaf7b..5c91348 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
> list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
> out:
> zone->free_area[order].nr_free++;
> + /* If the range spans two pageblocks, reset the migratetype. */
> + if (order > pageblock_order)
> + change_pageblock_range(page, order, migratetype);
> }
>
> static inline int free_pages_check(struct page *page)
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
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^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm: reset migratetype if the range spans two pageblocks
2015-10-16 10:06 ` Xishi Qiu
(?)
(?)
@ 2015-10-16 10:59 ` kbuild test robot
-1 siblings, 0 replies; 7+ messages in thread
From: kbuild test robot @ 2015-10-16 10:59 UTC (permalink / raw)
To: Xishi Qiu
Cc: kbuild-all, Andrew Morton, Vlastimil Babka, Mel Gorman, mhocko,
js1304, Johannes Weiner, alexander.h.duyck, zhongjiang, Linux MM,
LKML
[-- Attachment #1: Type: text/plain, Size: 1833 bytes --]
Hi Xishi,
[auto build test ERROR on v4.3-rc5 -- if it's inappropriate base, please suggest rules for selecting the more suitable base]
url: https://github.com/0day-ci/linux/commits/Xishi-Qiu/mm-reset-migratetype-if-the-range-spans-two-pageblocks/20151016-180949
config: i386-randconfig-s1-201541 (attached as .config)
reproduce:
# save the attached .config to linux build tree
make ARCH=i386
All error/warnings (new ones prefixed by >>):
mm/page_alloc.c: In function '__free_one_page':
>> mm/page_alloc.c:731:3: error: implicit declaration of function 'change_pageblock_range' [-Werror=implicit-function-declaration]
change_pageblock_range(page, order, migratetype);
^
mm/page_alloc.c: At top level:
>> mm/page_alloc.c:1515:13: warning: conflicting types for 'change_pageblock_range'
static void change_pageblock_range(struct page *pageblock_page,
^
>> mm/page_alloc.c:1515:13: error: static declaration of 'change_pageblock_range' follows non-static declaration
mm/page_alloc.c:731:3: note: previous implicit declaration of 'change_pageblock_range' was here
change_pageblock_range(page, order, migratetype);
^
cc1: some warnings being treated as errors
vim +/change_pageblock_range +731 mm/page_alloc.c
725
726 list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
727 out:
728 zone->free_area[order].nr_free++;
729 /* If the range spans two pageblocks, reset the migratetype. */
730 if (order > pageblock_order)
> 731 change_pageblock_range(page, order, migratetype);
732 }
733
734 static inline int free_pages_check(struct page *page)
---
0-DAY kernel test infrastructure Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all Intel Corporation
[-- Attachment #2: .config.gz --]
[-- Type: application/octet-stream, Size: 24803 bytes --]
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm: reset migratetype if the range spans two pageblocks
2015-10-16 10:06 ` Xishi Qiu
@ 2015-10-16 11:59 ` Vlastimil Babka
-1 siblings, 0 replies; 7+ messages in thread
From: Vlastimil Babka @ 2015-10-16 11:59 UTC (permalink / raw)
To: Xishi Qiu, Andrew Morton, Mel Gorman, mhocko, js1304,
Johannes Weiner, alexander.h.duyck, zhongjiang
Cc: Linux MM, LKML
On 10/16/2015 12:06 PM, Xishi Qiu wrote:
> __rmqueue_fallback() will change the migratetype of pageblock,
> so it is possible that two continuous pageblocks have different
> migratetypes.
>
> When freeing all pages of the two blocks, they will be merged
> to 4M, and added to the buddy list which the migratetype is the
> first pageblock's.
>
> If later alloc some pages and split the 4M, the second pageblock
> will be added to the buddy list, and the migratetype is the first
> pageblock's, so it is different from the its pageblock's.
>
> That means the page in buddy list's migratetype is different from
> the page in pageblock's migratetype. This will make confusion.
So what will be the bad effects of this confusion? There are many
situations where a free page (of any size) will be on different list
than the pageblock's migratetype.
In case of full free pageblock, it IIRC doesn't really matter on which
freelist it is, as the fallback scenarios for all migratetypes are
trivial and non-fragmenting (just grab the whole pageblock, which means
the migratetype is updated).
Maybe compaction will get it wrong when deciding which pageblocks are
suitable for scanning, but that's not critical.
> However,if we change the hotpath, it will be performance degradation,
> so any better ideas?
I don't see immediately a way to fix that outside of hotpath, and don't
see the reasons being strong enough to fix it in the hotpath.
>
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 48aaf7b..5c91348 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
> list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
> out:
> zone->free_area[order].nr_free++;
> + /* If the range spans two pageblocks, reset the migratetype. */
> + if (order > pageblock_order)
> + change_pageblock_range(page, order, migratetype);
> }
>
> static inline int free_pages_check(struct page *page)
>
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] mm: reset migratetype if the range spans two pageblocks
@ 2015-10-16 11:59 ` Vlastimil Babka
0 siblings, 0 replies; 7+ messages in thread
From: Vlastimil Babka @ 2015-10-16 11:59 UTC (permalink / raw)
To: Xishi Qiu, Andrew Morton, Mel Gorman, mhocko, js1304,
Johannes Weiner, alexander.h.duyck, zhongjiang
Cc: Linux MM, LKML
On 10/16/2015 12:06 PM, Xishi Qiu wrote:
> __rmqueue_fallback() will change the migratetype of pageblock,
> so it is possible that two continuous pageblocks have different
> migratetypes.
>
> When freeing all pages of the two blocks, they will be merged
> to 4M, and added to the buddy list which the migratetype is the
> first pageblock's.
>
> If later alloc some pages and split the 4M, the second pageblock
> will be added to the buddy list, and the migratetype is the first
> pageblock's, so it is different from the its pageblock's.
>
> That means the page in buddy list's migratetype is different from
> the page in pageblock's migratetype. This will make confusion.
So what will be the bad effects of this confusion? There are many
situations where a free page (of any size) will be on different list
than the pageblock's migratetype.
In case of full free pageblock, it IIRC doesn't really matter on which
freelist it is, as the fallback scenarios for all migratetypes are
trivial and non-fragmenting (just grab the whole pageblock, which means
the migratetype is updated).
Maybe compaction will get it wrong when deciding which pageblocks are
suitable for scanning, but that's not critical.
> However,if we change the hotpath, it will be performance degradation,
> so any better ideas?
I don't see immediately a way to fix that outside of hotpath, and don't
see the reasons being strong enough to fix it in the hotpath.
>
> Signed-off-by: Xishi Qiu <qiuxishi@huawei.com>
> ---
> mm/page_alloc.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 48aaf7b..5c91348 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -726,6 +726,9 @@ static inline void __free_one_page(struct page *page,
> list_add(&page->lru, &zone->free_area[order].free_list[migratetype]);
> out:
> zone->free_area[order].nr_free++;
> + /* If the range spans two pageblocks, reset the migratetype. */
> + if (order > pageblock_order)
> + change_pageblock_range(page, order, migratetype);
> }
>
> static inline int free_pages_check(struct page *page)
>
--
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^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2015-10-16 12:00 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2015-10-16 10:06 [PATCH] mm: reset migratetype if the range spans two pageblocks Xishi Qiu
2015-10-16 10:06 ` Xishi Qiu
2015-10-16 10:12 ` Xishi Qiu
2015-10-16 10:12 ` Xishi Qiu
2015-10-16 10:59 ` kbuild test robot
2015-10-16 11:59 ` Vlastimil Babka
2015-10-16 11:59 ` Vlastimil Babka
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