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mm,hugetlb: use folio fields in second tail page

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Patch series "mm,huge,rmap: unify and speed up compound mapcounts".


This patch (of 3):

We want to declare one more int in the first tail of a compound page: that
first tail page being valuable property, since every compound page has a
first tail, but perhaps no more than that.

No problem on 64-bit: there is already space for it.  No problem with
32-bit THPs: 5.18 commit 5232c63f46 ("mm: Make compound_pincount always
available") kindly cleared the space for it, apparently not realizing that
only 64-bit architectures enable CONFIG_THP_SWAP (whose use of tail
page->private might conflict) - but make sure of that in its Kconfig.

But hugetlb pages use tail page->private of the first tail page for a
subpool pointer, which will conflict; and they also use page->private of
the 2nd, 3rd and 4th tails.

Undo "mm: add private field of first tail to struct page and struct
folio"'s recent addition of private_1 to the folio tail: instead add
hugetlb_subpool, hugetlb_cgroup, hugetlb_cgroup_rsvd, hugetlb_hwpoison to
a second tail page of the folio: THP has long been using several fields of
that tail, so make better use of it for hugetlb too.  This is not how a
generic folio should be declared in future, but it is an effective
transitional way to make use of it.

Delete the SUBPAGE_INDEX stuff, but keep __NR_USED_SUBPAGE: now 3.

[hughd@google.com: prefix folio's page_1 and page_2 with double underscore,
  give folio's _flags_2 and _head_2 a line documentation each]
  Link: https://lkml.kernel.org/r/9e2cb6b-5b58-d3f2-b5ee-5f8a14e8f10@google.com
Link: https://lkml.kernel.org/r/5f52de70-975-e94f-f141-543765736181@google.com
Link: https://lkml.kernel.org/r/3818cc9a-9999-d064-d778-9c94c5911e6@google.com
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Zach O'Keefe <zokeefe@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Hugh Dickins
2022-11-02 18:48:45 -07:00
committed by Andrew Morton
parent 634ba645f9
commit dad6a5eb55
5 changed files with 67 additions and 68 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
include/linux/hugetlb_cgroup.h
View File

@@ -24,12 +24,10 @@ struct file_region;
#ifdef CONFIG_CGROUP_HUGETLB
/*
* Minimum page order trackable by hugetlb cgroup.
* At least 4 pages are necessary for all the tracking information.
* The second tail page (hpage[SUBPAGE_INDEX_CGROUP]) is the fault
* usage cgroup. The third tail page (hpage[SUBPAGE_INDEX_CGROUP_RSVD])
* is the reservation usage cgroup.
* At least 3 pages are necessary for all the tracking information.
* The second tail page contains all of the hugetlb-specific fields.
*/
#define HUGETLB_CGROUP_MIN_ORDER order_base_2(__MAX_CGROUP_SUBPAGE_INDEX + 1)
#define HUGETLB_CGROUP_MIN_ORDER order_base_2(__NR_USED_SUBPAGE)
enum hugetlb_memory_event {
HUGETLB_MAX,
@@ -69,21 +67,13 @@ struct hugetlb_cgroup {
static inline struct hugetlb_cgroup *
__hugetlb_cgroup_from_folio(struct folio *folio, bool rsvd)
{
struct page *tail;
VM_BUG_ON_FOLIO(!folio_test_hugetlb(folio), folio);
if (folio_order(folio) < HUGETLB_CGROUP_MIN_ORDER)
return NULL;
if (rsvd) {
tail = folio_page(folio, SUBPAGE_INDEX_CGROUP_RSVD);
return (void *)page_private(tail);
}
else {
tail = folio_page(folio, SUBPAGE_INDEX_CGROUP);
return (void *)page_private(tail);
}
if (rsvd)
return folio->_hugetlb_cgroup_rsvd;
else
return folio->_hugetlb_cgroup;
}
static inline struct hugetlb_cgroup *hugetlb_cgroup_from_folio(struct folio *folio)
@@ -101,15 +91,12 @@ static inline void __set_hugetlb_cgroup(struct folio *folio,
struct hugetlb_cgroup *h_cg, bool rsvd)
{
VM_BUG_ON_FOLIO(!folio_test_hugetlb(folio), folio);
if (folio_order(folio) < HUGETLB_CGROUP_MIN_ORDER)
return;
if (rsvd)
set_page_private(folio_page(folio, SUBPAGE_INDEX_CGROUP_RSVD),
(unsigned long)h_cg);
folio->_hugetlb_cgroup_rsvd = h_cg;
else
set_page_private(folio_page(folio, SUBPAGE_INDEX_CGROUP),
(unsigned long)h_cg);
folio->_hugetlb_cgroup = h_cg;
}
static inline void set_hugetlb_cgroup(struct folio *folio,