On 2022-01-19 20:06, 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(MAX_ORDER_NR_PAEGS, pageblock_nr_pages) 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.
Hi Zi Yan,
I had to re-read this several times as I found this a bit misleading.
I was mainly confused by the fact that memory_hotplug does isolation on
PAGES_PER_SECTION granularity, and reading the above seems to indicate
that either do it at MAX_ORDER_NR_PAGES or at pageblock_nr_pages
granularity.
True is that start_isolate_page_range() expects the range to be
pageblock aligned and works in pageblock_nr_pages chunks, but I do not
think that is what you meant to say here.
Now, to the change itself, below:
@@ -47,8 +51,8 @@ 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 = first_pfn; pfn < last_pfn; pfn++) {
You already did pfn = first_pfn before.
/**
* start_isolate_page_range() - make page-allocation-type of range of
pages to
* be MIGRATE_ISOLATE.
- * @start_pfn: The lower PFN of the range to be isolated.
- * @end_pfn: The upper PFN of the range to be isolated.
+ * @start_pfn: The lower PFN of the range to be checked for
+ * possibility of isolation.
+ * @end_pfn: The upper PFN of the range to be checked for
+ * possibility of isolation.
+ * @isolate_start: The lower PFN of the range to be isolated.
+ * @isolate_end: The upper PFN of the range to be isolated.
So, what does "possibility" means here. I think this need to be
clarified a bit better.
From what you pointed out in the commit message I think what you are
doing is:
- alloc_contig_range() gets a range to be isolated.
- then you pass two ranges to start_isolate_page_range()
(start_pfn, end_pfn]: which is the unaligned range you got in
alloc_contig_range()
(isolate_start, isolate_end]: which got aligned to, let's say, to
MAX_ORDER_NR_PAGES
Now, most likely, (start_pfn, end_pfn] only covers a sub-range of
(isolate_start, isolate_end], and that
sub-range is what you really want to isolate (so (start_pfn, end_pfn])?
If so, should not the names be reversed?
--
Oscar Salvador
SUSE Labs
