On 2024/8/18 7:58, Zi Yan wrote:
On 17 Aug 2024, at 2:13, Kefeng Wang wrote:
On 2024/8/17 3:45, David Hildenbrand wrote:
On 16.08.24 13:30, Kefeng Wang wrote:
On 2024/8/16 18:11, David Hildenbrand wrote:
On 16.08.24 06:06, Kefeng Wang wrote:
The gigantic page size may larger than memory block size, so memory
offline always fails in this case after commit b2c9e2fbba32 ("mm: make
alloc_contig_range work at pageblock granularity"),
offline_pages
start_isolate_page_range
start_isolate_page_range(isolate_before=true)
isolate [isolate_start, isolate_start + pageblock_nr_pages)
start_isolate_page_range(isolate_before=false)
isolate [isolate_end - pageblock_nr_pages, isolate_end) pageblock
__alloc_contig_migrate_range
isolate_migratepages_range
isolate_migratepages_block
isolate_or_dissolve_huge_page
if (hstate_is_gigantic(h))
return -ENOMEM;
In fact, we don't need to migrate page in page range isolation, for
memory offline path, there is do_migrate_range() to move the pages.
For contig allocation, there is another __alloc_contig_migrate_range()
after isolation to migrate the pages. So fix issue by skipping the
__alloc_contig_migrate_range() in isolate_single_pageblock().
...
Please distill some of that in the patch description. Right now you only talk about memory offlining and don't cover why alloc_contig_range() is fine as well with this change.
Borrowing some word from Zi,
PageHuge(gigantic) can bigger than a pageblock, the gigantic PageHuge is freed as order-0. This means MIGRATE_ISOLATE pageblocks will get to the right free list after __alloc_contig_migrate_range(), the one after
start_isolate_page_range() for alloc_contig_range(), this is same as in
memory offline, it has own path to isolate/migrate used page and dissolve the free hugepages, so the migration code in isolate_single_pageblock() is not needed, let's cleanup it and which also fix the above the issue.
Please correct me or help to write better description, thanks.
How about?
Gigantic PageHuge is bigger than a pageblock, but since it is freed as order-0 pages,
its pageblocks after being freed will get to the right free list. There is no need
to have special handling code for them in start_isolate_page_range(). For both
alloc_contig_range() and memory offline cases, the migration code after
start_isolate_page_range() will be able to migrate gigantic PageHuge when possible.
Let's clean up start_isolate_page_range() and fix the aforementioned memory offline
failure issue all together.
Thanks Zi, it is better, will update.
--
Best Regards,
Yan, Zi
