mm/khugepaged: use minimal bits to store num page < HPAGE_PMD_NR

Minimally, node_load[] entries just need to be able to hold the maximum
value of HPAGE_PMD_NR, which is compile-time defined per-arch based on
PMD_SHIFT and PAGE_SHIFT.  node_load[] is only written either via
memset(), or with via post-increment.  struct collapse_control may be
allocated via kmalloc() in other collapse contexts, and MAX_NUMNODES may
be arbitrarily large.  #define the underlying type of node_load[] based
off HPAGE_PMD_NR to avoid excessive memory allocated for this struct.

Link: https://lkml.kernel.org/r/20220720140603.1958773-2-zokeefe@google.com
Link: https://lore.kernel.org/linux-mm/Ys2CeIm%2FQmQwWh9a@google.com/
Fixes: 3b07f3bb225a ("mm/khugepaged: add struct collapse_control")
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: Chris Kennelly <ckennelly@google.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Matt Turner <mattst88@gmail.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Pavel Begunkov <asml.silence@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Rongwei Wang <rongwei.wang@linux.alibaba.com>
Cc: SeongJae Park <sj@kernel.org>
Cc: Song Liu <songliubraving@fb.com>
Cc: "Souptick Joarder (HPE)" <jrdr.linux@gmail.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index c21eb83eb7fbd6d5035169341c7ad828406e5ba4..5fce308b6472c012c31fffa1da29913a1b4eec68 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -87,8 +87,11 @@ static struct kmem_cache *mm_slot_cache __read_mostly;
 
 struct collapse_control {
        /* Num pages scanned per node */
-       int node_load[MAX_NUMNODES];
-
+#if HPAGE_PMD_ORDER < 16
+       u16 node_load[MAX_NUMNODES];
+#else
+       u32 node_load[MAX_NUMNODES];
+#endif
        /* Last target selected in khugepaged_find_target_node() */
        int last_target_node;
 };