From: Srikar Dronamraju Date: Sat, 10 Sep 2016 10:34:10 +0000 (+1000) Subject: mm: introduce arch_reserved_kernel_pages() X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=433c240a2c34fa998e68c796d90d8ff6f2cb62c7;p=deliverable%2Flinux.git 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/1472476010-4709-2-git-send-email-srikar@linux.vnet.ibm.com Signed-off-by: Srikar Dronamraju Suggested-by: Mel Gorman Cc: Vlastimil Babka Cc: Michal Hocko Cc: Michael Ellerman Cc: Mahesh Salgaonkar Cc: Hari Bathini Cc: Dave Hansen Cc: Balbir Singh Cc: Benjamin Herrenschmidt Signed-off-by: Andrew Morton --- diff --git a/include/linux/mm.h b/include/linux/mm.h index f4e639e849a6..569514cb3ed1 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1924,6 +1924,9 @@ extern void show_mem(unsigned int flags); extern long si_mem_available(void); extern void si_meminfo(struct sysinfo * val); extern void si_meminfo_node(struct sysinfo *val, int nid); +#ifdef __HAVE_ARCH_RESERVED_KERNEL_PAGES +extern unsigned long arch_reserved_kernel_pages(void); +#endif extern __printf(3, 4) void warn_alloc_failed(gfp_t gfp_mask, unsigned int order, diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 3c69879193a4..7e48ee52685b 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -6944,6 +6944,17 @@ static int __init set_hashdist(char *str) __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 @@ -6968,6 +6979,7 @@ void *__init alloc_large_system_hash(const char *tablename, 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)