On 12 Apr 2022, at 9:10, David Hildenbrand wrote:
> On 06.04.22 17:18, Zi Yan wrote:
>> From: Zi Yan <ziy@xxxxxxxxxx>
>>
>> Enable set_migratetype_isolate() to check specified sub-range for
>> unmovable pages during isolation. Page isolation is done
>> at MAX_ORDER_NR_PAEGS granularity, but not all pages within that
>> granularity are intended to be isolated. For example,
>> alloc_contig_range(), which uses page isolation, allows ranges without
>> alignment. This commit makes unmovable page check only look for
>> interesting pages, so that page isolation can succeed for any
>> non-overlapping ranges.
>>
>> Signed-off-by: Zi Yan <ziy@xxxxxxxxxx>
>> ---
>
> [...]
>
>> /*
>> - * This function checks whether pageblock includes unmovable pages or not.
>> + * This function checks whether the range [start_pfn, end_pfn) includes
>> + * unmovable pages or not. The range must fall into a single pageblock and
>> + * consequently belong to a single zone.
>> *
>> * PageLRU check without isolation or lru_lock could race so that
>> * MIGRATE_MOVABLE block might include unmovable pages. And __PageMovable
>> @@ -28,12 +30,14 @@
>> * cannot get removed (e.g., via memory unplug) concurrently.
>> *
>> */
>> -static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>> - int migratetype, int flags)
>> +static struct page *has_unmovable_pages(unsigned long start_pfn, unsigned long end_pfn,
>> + int migratetype, int flags)
>> {
>> - unsigned long iter = 0;
>> - unsigned long pfn = page_to_pfn(page);
>> - unsigned long offset = pfn % pageblock_nr_pages;
>> + unsigned long pfn = start_pfn;
>> + struct page *page = pfn_to_page(pfn);
>
>
> Just do
>
> struct page *page = pfn_to_page(start_pfn);
> struct zone *zone = page_zone(page);
>
> here. No need to lookup the zone again in the loop because, as you
> document "must ... belong to a single zone.".
>
> Then, there is also no need to initialize "pfn" here. In the loop header
> is sufficient.
>
Sure.
>> +
>> + VM_BUG_ON(ALIGN_DOWN(start_pfn, pageblock_nr_pages) !=
>> + ALIGN_DOWN(end_pfn - 1, pageblock_nr_pages));
>>
>> if (is_migrate_cma_page(page)) {
>> /*
>> @@ -47,8 +51,11 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>> return page;
>> }
>>
>> - for (; iter < pageblock_nr_pages - offset; iter++) {
>> - page = pfn_to_page(pfn + iter);
>> + for (pfn = start_pfn; pfn < end_pfn; pfn++) {
>> + struct zone *zone;
>> +
>> + page = pfn_to_page(pfn);
>> + zone = page_zone(page);
>>
>> /*
>> * Both, bootmem allocations and memory holes are marked
>> @@ -85,7 +92,7 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>> }
>>
>> skip_pages = compound_nr(head) - (page - head);
>> - iter += skip_pages - 1;
>> + pfn += skip_pages - 1;
>> continue;
>> }
>>
>> @@ -97,7 +104,7 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>> */
>> if (!page_ref_count(page)) {
>> if (PageBuddy(page))
>> - iter += (1 << buddy_order(page)) - 1;
>> + pfn += (1 << buddy_order(page)) - 1;
>> continue;
>> }
>>
>> @@ -134,11 +141,18 @@ static struct page *has_unmovable_pages(struct zone *zone, struct page *page,
>> return NULL;
>> }
>>
>> -static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags)
>> +/*
>> + * This function set pageblock migratetype to isolate if no unmovable page is
>> + * present in [start_pfn, end_pfn). The pageblock must intersect with
>> + * [start_pfn, end_pfn).
>> + */
>> +static int set_migratetype_isolate(struct page *page, int migratetype, int isol_flags,
>> + unsigned long start_pfn, unsigned long end_pfn)
>
> I think we might be able do better, eventually not passing start_pfn at
> all. Hmm.
IMHO, having start_pfn and end_pfn in the parameter list would make the
interface easier to understand. Otherwise if we remove start_pfn,
the caller needs to adjust @page to be within the range of [start_pfn,
end_pfn)
>
> I think we want to pull out the
> start_isolate_page_range()/undo_isolate_page_range() interface change
> into a separate patch.
You mean a patch just adding
unsigned long isolate_start = pfn_max_align_down(start_pfn);
unsigned long isolate_end = pfn_max_align_up(end_pfn);
in start_isolate_page_range()/undo_isolate_page_range()?
Yes I can do that.
>
> Let me try to give it a shot, I'll try hacking something up real quick
> to see if we can do better.
Sure. Thanks.
--
Best Regards,
Yan, Zi
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