mm: introduce arch_reserved_kernel_pages()
Currently arch specific code can reserve memory blocks but
alloc_large_system_hash() may not take it into consideration when sizing
the hashes. This can lead to bigger hash than required and lead to no
available memory for other purposes. This is specifically true for
systems with CONFIG_DEFERRED_STRUCT_PAGE_INIT enabled.
One approach to solve this problem would be to walk through the memblock
regions and calculate the available memory and base the size of hash
system on the available memory.
The other approach would be to depend on the architecture to provide the
number of pages that are reserved. This change provides hooks to allow
the architecture to provide the required info.
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Srikar Dronamraju <[email protected]>
Suggested-by: Mel Gorman <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Mahesh Salgaonkar <[email protected]>
Cc: Hari Bathini <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Balbir Singh <[email protected]>
Cc: Benjamin Herrenschmidt <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index f6a5a22..e00f545 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -6940,6 +6940,17 @@
__setup("hashdist=", set_hashdist);
#endif
+#ifndef __HAVE_ARCH_RESERVED_KERNEL_PAGES
+/*
+ * Returns the number of pages that arch has reserved but
+ * is not known to alloc_large_system_hash().
+ */
+static unsigned long __init arch_reserved_kernel_pages(void)
+{
+ return 0;
+}
+#endif
+
/*
* allocate a large system hash table from bootmem
* - it is assumed that the hash table must contain an exact power-of-2
@@ -6964,6 +6975,7 @@
if (!numentries) {
/* round applicable memory size up to nearest megabyte */
numentries = nr_kernel_pages;
+ numentries -= arch_reserved_kernel_pages();
/* It isn't necessary when PAGE_SIZE >= 1MB */
if (PAGE_SHIFT < 20)
