* [PATCH] mm/page_alloc: Do not isolate redundant pageblock
@ 2020-11-27 14:19 Muchun Song
2020-11-27 15:17 ` Vlastimil Babka
2020-11-27 16:54 ` David Hildenbrand
0 siblings, 2 replies; 5+ messages in thread
From: Muchun Song @ 2020-11-27 14:19 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, Muchun Song
Current pageblock isolation logic could isolate each pageblock individually
since commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated
and other pageblocks"). So we not need to concern about page allocator
merges buddies from different pageblocks and changes MIGRATE_ISOLATE to
some other migration type.
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
---
mm/page_alloc.c | 26 ++++++++------------------
1 file changed, 8 insertions(+), 18 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cefbef32bf4a..608a2c2b8ab7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8313,16 +8313,14 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
}
#ifdef CONFIG_CONTIG_ALLOC
-static unsigned long pfn_max_align_down(unsigned long pfn)
+static unsigned long pfn_align_down(unsigned long pfn)
{
- return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
- pageblock_nr_pages) - 1);
+ return pfn & ~(pageblock_nr_pages - 1);
}
-static unsigned long pfn_max_align_up(unsigned long pfn)
+static unsigned long pfn_align_up(unsigned long pfn)
{
- return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
- pageblock_nr_pages));
+ return ALIGN(pfn, pageblock_nr_pages);
}
/* [start, end) must belong to a single zone. */
@@ -8415,14 +8413,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
INIT_LIST_HEAD(&cc.migratepages);
/*
- * What we do here is we mark all pageblocks in range as
- * MIGRATE_ISOLATE. Because pageblock and max order pages may
- * have different sizes, and due to the way page allocator
- * work, we align the range to biggest of the two pages so
- * that page allocator won't try to merge buddies from
- * different pageblocks and change MIGRATE_ISOLATE to some
- * other migration type.
- *
* Once the pageblocks are marked as MIGRATE_ISOLATE, we
* migrate the pages from an unaligned range (ie. pages that
* we are interested in). This will put all the pages in
@@ -8438,8 +8428,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
* put back to page allocator so that buddy can use them.
*/
- ret = start_isolate_page_range(pfn_max_align_down(start),
- pfn_max_align_up(end), migratetype, 0);
+ ret = start_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
+ migratetype, 0);
if (ret)
return ret;
@@ -8522,8 +8512,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
free_contig_range(end, outer_end - end);
done:
- undo_isolate_page_range(pfn_max_align_down(start),
- pfn_max_align_up(end), migratetype);
+ undo_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
+ migratetype);
return ret;
}
EXPORT_SYMBOL(alloc_contig_range);
--
2.11.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_alloc: Do not isolate redundant pageblock
2020-11-27 14:19 [PATCH] mm/page_alloc: Do not isolate redundant pageblock Muchun Song
@ 2020-11-27 15:17 ` Vlastimil Babka
2020-11-27 15:43 ` [External] " Muchun Song
2020-11-27 16:54 ` David Hildenbrand
1 sibling, 1 reply; 5+ messages in thread
From: Vlastimil Babka @ 2020-11-27 15:17 UTC (permalink / raw)
To: Muchun Song, akpm; +Cc: linux-mm, linux-kernel
On 11/27/20 3:19 PM, Muchun Song wrote:
> Current pageblock isolation logic could isolate each pageblock individually
> since commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated
> and other pageblocks"). So we not need to concern about page allocator
> merges buddies from different pageblocks and changes MIGRATE_ISOLATE to
> some other migration type.
Yeah, that should be the case now.
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> mm/page_alloc.c | 26 ++++++++------------------
> 1 file changed, 8 insertions(+), 18 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cefbef32bf4a..608a2c2b8ab7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8313,16 +8313,14 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
> }
>
> #ifdef CONFIG_CONTIG_ALLOC
> -static unsigned long pfn_max_align_down(unsigned long pfn)
> +static unsigned long pfn_align_down(unsigned long pfn)
> {
> - return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
> - pageblock_nr_pages) - 1);
> + return pfn & ~(pageblock_nr_pages - 1);
> }
>
> -static unsigned long pfn_max_align_up(unsigned long pfn)
> +static unsigned long pfn_align_up(unsigned long pfn)
> {
> - return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
> - pageblock_nr_pages));
> + return ALIGN(pfn, pageblock_nr_pages);
> }
How bout just removing these wrappers completely and using ALIGN and ALIGN_DOWN
directly, as there are just two uses for each?
> /* [start, end) must belong to a single zone. */
> @@ -8415,14 +8413,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> INIT_LIST_HEAD(&cc.migratepages);
>
> /*
> - * What we do here is we mark all pageblocks in range as
> - * MIGRATE_ISOLATE. Because pageblock and max order pages may
> - * have different sizes, and due to the way page allocator
> - * work, we align the range to biggest of the two pages so
> - * that page allocator won't try to merge buddies from
> - * different pageblocks and change MIGRATE_ISOLATE to some
> - * other migration type.
> - *
> * Once the pageblocks are marked as MIGRATE_ISOLATE, we
> * migrate the pages from an unaligned range (ie. pages that
> * we are interested in). This will put all the pages in
> @@ -8438,8 +8428,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> * put back to page allocator so that buddy can use them.
> */
>
> - ret = start_isolate_page_range(pfn_max_align_down(start),
> - pfn_max_align_up(end), migratetype, 0);
> + ret = start_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
> + migratetype, 0);
> if (ret)
> return ret;
>
> @@ -8522,8 +8512,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> free_contig_range(end, outer_end - end);
>
> done:
> - undo_isolate_page_range(pfn_max_align_down(start),
> - pfn_max_align_up(end), migratetype);
> + undo_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
> + migratetype);
> return ret;
> }
> EXPORT_SYMBOL(alloc_contig_range);
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [External] Re: [PATCH] mm/page_alloc: Do not isolate redundant pageblock
2020-11-27 15:17 ` Vlastimil Babka
@ 2020-11-27 15:43 ` Muchun Song
0 siblings, 0 replies; 5+ messages in thread
From: Muchun Song @ 2020-11-27 15:43 UTC (permalink / raw)
To: Vlastimil Babka; +Cc: Andrew Morton, Linux Memory Management List, LKML
On Fri, Nov 27, 2020 at 11:17 PM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> On 11/27/20 3:19 PM, Muchun Song wrote:
> > Current pageblock isolation logic could isolate each pageblock individually
> > since commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated
> > and other pageblocks"). So we not need to concern about page allocator
> > merges buddies from different pageblocks and changes MIGRATE_ISOLATE to
> > some other migration type.
>
> Yeah, that should be the case now.
>
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> > ---
> > mm/page_alloc.c | 26 ++++++++------------------
> > 1 file changed, 8 insertions(+), 18 deletions(-)
> >
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index cefbef32bf4a..608a2c2b8ab7 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -8313,16 +8313,14 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
> > }
> >
> > #ifdef CONFIG_CONTIG_ALLOC
> > -static unsigned long pfn_max_align_down(unsigned long pfn)
> > +static unsigned long pfn_align_down(unsigned long pfn)
> > {
> > - return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
> > - pageblock_nr_pages) - 1);
> > + return pfn & ~(pageblock_nr_pages - 1);
> > }
> >
> > -static unsigned long pfn_max_align_up(unsigned long pfn)
> > +static unsigned long pfn_align_up(unsigned long pfn)
> > {
> > - return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
> > - pageblock_nr_pages));
> > + return ALIGN(pfn, pageblock_nr_pages);
> > }
>
> How bout just removing these wrappers completely and using ALIGN and ALIGN_DOWN
> directly, as there are just two uses for each?
Sounds good to me. Will do.
>
> > /* [start, end) must belong to a single zone. */
> > @@ -8415,14 +8413,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> > INIT_LIST_HEAD(&cc.migratepages);
> >
> > /*
> > - * What we do here is we mark all pageblocks in range as
> > - * MIGRATE_ISOLATE. Because pageblock and max order pages may
> > - * have different sizes, and due to the way page allocator
> > - * work, we align the range to biggest of the two pages so
> > - * that page allocator won't try to merge buddies from
> > - * different pageblocks and change MIGRATE_ISOLATE to some
> > - * other migration type.
> > - *
> > * Once the pageblocks are marked as MIGRATE_ISOLATE, we
> > * migrate the pages from an unaligned range (ie. pages that
> > * we are interested in). This will put all the pages in
> > @@ -8438,8 +8428,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> > * put back to page allocator so that buddy can use them.
> > */
> >
> > - ret = start_isolate_page_range(pfn_max_align_down(start),
> > - pfn_max_align_up(end), migratetype, 0);
> > + ret = start_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
> > + migratetype, 0);
> > if (ret)
> > return ret;
> >
> > @@ -8522,8 +8512,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> > free_contig_range(end, outer_end - end);
> >
> > done:
> > - undo_isolate_page_range(pfn_max_align_down(start),
> > - pfn_max_align_up(end), migratetype);
> > + undo_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
> > + migratetype);
> > return ret;
> > }
> > EXPORT_SYMBOL(alloc_contig_range);
> >
>
--
Yours,
Muchun
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_alloc: Do not isolate redundant pageblock
2020-11-27 14:19 [PATCH] mm/page_alloc: Do not isolate redundant pageblock Muchun Song
2020-11-27 15:17 ` Vlastimil Babka
@ 2020-11-27 16:54 ` David Hildenbrand
2020-11-27 16:56 ` David Hildenbrand
1 sibling, 1 reply; 5+ messages in thread
From: David Hildenbrand @ 2020-11-27 16:54 UTC (permalink / raw)
To: Muchun Song, akpm; +Cc: linux-mm, linux-kernel
On 27.11.20 15:19, Muchun Song wrote:
> Current pageblock isolation logic could isolate each pageblock individually
> since commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated
> and other pageblocks"). So we not need to concern about page allocator
> merges buddies from different pageblocks and changes MIGRATE_ISOLATE to
> some other migration type.
>
> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
> ---
> mm/page_alloc.c | 26 ++++++++------------------
> 1 file changed, 8 insertions(+), 18 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cefbef32bf4a..608a2c2b8ab7 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -8313,16 +8313,14 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
> }
>
> #ifdef CONFIG_CONTIG_ALLOC
> -static unsigned long pfn_max_align_down(unsigned long pfn)
> +static unsigned long pfn_align_down(unsigned long pfn)
> {
> - return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
> - pageblock_nr_pages) - 1);
> + return pfn & ~(pageblock_nr_pages - 1);
> }
>
> -static unsigned long pfn_max_align_up(unsigned long pfn)
> +static unsigned long pfn_align_up(unsigned long pfn)
> {
> - return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
> - pageblock_nr_pages));
> + return ALIGN(pfn, pageblock_nr_pages);
> }
>
> /* [start, end) must belong to a single zone. */
> @@ -8415,14 +8413,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> INIT_LIST_HEAD(&cc.migratepages);
>
> /*
> - * What we do here is we mark all pageblocks in range as
> - * MIGRATE_ISOLATE. Because pageblock and max order pages may
> - * have different sizes, and due to the way page allocator
> - * work, we align the range to biggest of the two pages so
> - * that page allocator won't try to merge buddies from
> - * different pageblocks and change MIGRATE_ISOLATE to some
> - * other migration type.
> - *
> * Once the pageblocks are marked as MIGRATE_ISOLATE, we
> * migrate the pages from an unaligned range (ie. pages that
> * we are interested in). This will put all the pages in
> @@ -8438,8 +8428,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> * put back to page allocator so that buddy can use them.
> */
>
> - ret = start_isolate_page_range(pfn_max_align_down(start),
> - pfn_max_align_up(end), migratetype, 0);
> + ret = start_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
> + migratetype, 0);
> if (ret)
> return ret;
>
> @@ -8522,8 +8512,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
> free_contig_range(end, outer_end - end);
>
> done:
> - undo_isolate_page_range(pfn_max_align_down(start),
> - pfn_max_align_up(end), migratetype);
> + undo_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
> + migratetype);
> return ret;
> }
> EXPORT_SYMBOL(alloc_contig_range);
>
Last time I checked, set_migratetype_isolate()->has_unmovable_pages()
was not prepared for that in case of !CMA and !ZONE_MOVABLE.
Assume you have an unmovable MAX_ORDER - 1 page that spans two
pageblocks (e.g., x86-64). Assume you try to isolate the second
pageblock. IIRC, you would answer "yes", as the refcount of all involved
pages is 0.
How did you test this works as expected?
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] mm/page_alloc: Do not isolate redundant pageblock
2020-11-27 16:54 ` David Hildenbrand
@ 2020-11-27 16:56 ` David Hildenbrand
0 siblings, 0 replies; 5+ messages in thread
From: David Hildenbrand @ 2020-11-27 16:56 UTC (permalink / raw)
To: Muchun Song, akpm; +Cc: linux-mm, linux-kernel
On 27.11.20 17:54, David Hildenbrand wrote:
> On 27.11.20 15:19, Muchun Song wrote:
>> Current pageblock isolation logic could isolate each pageblock individually
>> since commit d9dddbf55667 ("mm/page_alloc: prevent merging between isolated
>> and other pageblocks"). So we not need to concern about page allocator
>> merges buddies from different pageblocks and changes MIGRATE_ISOLATE to
>> some other migration type.
>>
>> Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>> ---
>> mm/page_alloc.c | 26 ++++++++------------------
>> 1 file changed, 8 insertions(+), 18 deletions(-)
>>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index cefbef32bf4a..608a2c2b8ab7 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -8313,16 +8313,14 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>> }
>>
>> #ifdef CONFIG_CONTIG_ALLOC
>> -static unsigned long pfn_max_align_down(unsigned long pfn)
>> +static unsigned long pfn_align_down(unsigned long pfn)
>> {
>> - return pfn & ~(max_t(unsigned long, MAX_ORDER_NR_PAGES,
>> - pageblock_nr_pages) - 1);
>> + return pfn & ~(pageblock_nr_pages - 1);
>> }
>>
>> -static unsigned long pfn_max_align_up(unsigned long pfn)
>> +static unsigned long pfn_align_up(unsigned long pfn)
>> {
>> - return ALIGN(pfn, max_t(unsigned long, MAX_ORDER_NR_PAGES,
>> - pageblock_nr_pages));
>> + return ALIGN(pfn, pageblock_nr_pages);
>> }
>>
>> /* [start, end) must belong to a single zone. */
>> @@ -8415,14 +8413,6 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>> INIT_LIST_HEAD(&cc.migratepages);
>>
>> /*
>> - * What we do here is we mark all pageblocks in range as
>> - * MIGRATE_ISOLATE. Because pageblock and max order pages may
>> - * have different sizes, and due to the way page allocator
>> - * work, we align the range to biggest of the two pages so
>> - * that page allocator won't try to merge buddies from
>> - * different pageblocks and change MIGRATE_ISOLATE to some
>> - * other migration type.
>> - *
>> * Once the pageblocks are marked as MIGRATE_ISOLATE, we
>> * migrate the pages from an unaligned range (ie. pages that
>> * we are interested in). This will put all the pages in
>> @@ -8438,8 +8428,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>> * put back to page allocator so that buddy can use them.
>> */
>>
>> - ret = start_isolate_page_range(pfn_max_align_down(start),
>> - pfn_max_align_up(end), migratetype, 0);
>> + ret = start_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
>> + migratetype, 0);
>> if (ret)
>> return ret;
>>
>> @@ -8522,8 +8512,8 @@ int alloc_contig_range(unsigned long start, unsigned long end,
>> free_contig_range(end, outer_end - end);
>>
>> done:
>> - undo_isolate_page_range(pfn_max_align_down(start),
>> - pfn_max_align_up(end), migratetype);
>> + undo_isolate_page_range(pfn_align_down(start), pfn_align_up(end),
>> + migratetype);
>> return ret;
>> }
>> EXPORT_SYMBOL(alloc_contig_range);
>>
>
> Last time I checked, set_migratetype_isolate()->has_unmovable_pages()
> was not prepared for that in case of !CMA and !ZONE_MOVABLE.
>
> Assume you have an unmovable MAX_ORDER - 1 page that spans two
> pageblocks (e.g., x86-64). Assume you try to isolate the second
> pageblock. IIRC, you would answer "yes", as the refcount of all involved
> pages is 0.
>
>
> How did you test this works as expected?
>
And I forgot to mention, in case it's a movable MAX_ORDER - 1 page (or
simply free), would __alloc_contig_migrate_range() do the right thing
and migrate the whole page?
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 5+ messages in thread
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2020-11-27 14:19 [PATCH] mm/page_alloc: Do not isolate redundant pageblock Muchun Song
2020-11-27 15:17 ` Vlastimil Babka
2020-11-27 15:43 ` [External] " Muchun Song
2020-11-27 16:54 ` David Hildenbrand
2020-11-27 16:56 ` David Hildenbrand
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