diff options
author | David Hildenbrand <david@redhat.com> | 2020-10-14 02:55:17 +0300 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2020-10-14 04:38:32 +0300 |
commit | c9c510dc2964420038f8527125a2cd5d8fb79cb6 (patch) | |
tree | 56083f5c25eae625922eb1ac19c978de074adfbd /mm/page_alloc.c | |
parent | be4f1ae978ffe98cc95ec49ceb95386fb4474974 (diff) | |
download | linux-c9c510dc2964420038f8527125a2cd5d8fb79cb6.tar.xz |
mm/page_alloc: tweak comments in has_unmovable_pages()
Patch series "mm / virtio-mem: support ZONE_MOVABLE", v5.
When introducing virtio-mem, the semantics of ZONE_MOVABLE were rather
unclear, which is why we special-cased ZONE_MOVABLE such that partially
plugged blocks would never end up in ZONE_MOVABLE.
Now that the semantics are much clearer (and are documented in patch #6),
let's support partially plugged memory blocks in ZONE_MOVABLE, allowing
partially plugged memory blocks to be online to ZONE_MOVABLE and also
unplugging from such memory blocks. This avoids surprises when onlining
of memory blocks suddenly fails, just because they are not completely
populated by virtio-mem (yet).
This is especially helpful for testing, but also paves the way for
virtio-mem optimizations, allowing more memory to get reliably unplugged.
Cleanup has_unmovable_pages() and set_migratetype_isolate(), providing
better documentation of how ZONE_MOVABLE interacts with different kind of
unmovable pages (memory offlining vs. alloc_contig_range()).
This patch (of 6):
Let's move the split comment regarding bootmem allocations and memory
holes, especially in the context of ZONE_MOVABLE, to the PageReserved()
check.
Signed-off-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Qian Cai <cai@lca.pw>
Link: http://lkml.kernel.org/r/20200816125333.7434-1-david@redhat.com
Link: http://lkml.kernel.org/r/20200816125333.7434-2-david@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/page_alloc.c')
-rw-r--r-- | mm/page_alloc.c | 22 |
1 files changed, 6 insertions, 16 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 780c8f023b28..ff0b14b0e8d7 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -8235,14 +8235,6 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, unsigned long iter = 0; unsigned long pfn = page_to_pfn(page); - /* - * TODO we could make this much more efficient by not checking every - * page in the range if we know all of them are in MOVABLE_ZONE and - * that the movable zone guarantees that pages are migratable but - * the later is not the case right now unfortunatelly. E.g. movablecore - * can still lead to having bootmem allocations in zone_movable. - */ - if (is_migrate_cma_page(page)) { /* * CMA allocations (alloc_contig_range) really need to mark @@ -8261,6 +8253,12 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, page = pfn_to_page(pfn + iter); + /* + * Both, bootmem allocations and memory holes are marked + * PG_reserved and are unmovable. We can even have unmovable + * allocations inside ZONE_MOVABLE, for example when + * specifying "movablecore". + */ if (PageReserved(page)) return page; @@ -8334,14 +8332,6 @@ struct page *has_unmovable_pages(struct zone *zone, struct page *page, * it. But now, memory offline itself doesn't call * shrink_node_slabs() and it still to be fixed. */ - /* - * If the page is not RAM, page_count()should be 0. - * we don't need more check. This is an _used_ not-movable page. - * - * The problematic thing here is PG_reserved pages. PG_reserved - * is set to both of a memory hole page and a _used_ kernel - * page at boot. - */ return page; } return NULL; |