The patch titled
Subject: mm/page_alloc: tweak comments in has_unmovable_pages()
has been added to the -mm tree. Its filename is
mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20200816125333.7434-1-david@xxxxxxxxxx
Link: http://lkml.kernel.org/r/20200816125333.7434-2-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxx>
Cc: Qian Cai <cai@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 22 ++++++----------------
1 file changed, 6 insertions(+), 16 deletions(-)
--- a/mm/page_alloc.c~mm-page_alloc-tweak-comments-in-has_unmovable_pages
+++ a/mm/page_alloc.c
@@ -8219,14 +8219,6 @@ struct page *has_unmovable_pages(struct
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
@@ -8245,6 +8237,12 @@ struct page *has_unmovable_pages(struct
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;
@@ -8318,14 +8316,6 @@ struct page *has_unmovable_pages(struct
* 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;
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-page_alloc-tweak-comments-in-has_unmovable_pages.patch
mm-page_isolation-exit-early-when-pageblock-is-isolated-in-set_migratetype_isolate.patch
mm-page_isolation-drop-warn_on_once-in-set_migratetype_isolate.patch
mm-page_isolation-cleanup-set_migratetype_isolate.patch
virtio-mem-dont-special-case-zone_movable.patch
mm-document-semantics-of-zone_movable.patch
