Commit 3749a8f0 authored by Pavel Tatashin's avatar Pavel Tatashin Committed by Linus Torvalds
Browse files

mm: zero hash tables in allocator 

Add a new flag HASH_ZERO which when provided grantees that the hash
table that is returned by alloc_large_system_hash() is zeroed.  In most
cases that is what is needed by the caller.  Use page level allocator's
__GFP_ZERO flags to zero the memory.  It is using memset() which is
efficient method to zero memory and is optimized for most platforms.

Link: http://lkml.kernel.org/r/1488432825-92126-3-git-send-email-pasha.tatashin@oracle.com


Signed-off-by: default avatarPavel Tatashin <pasha.tatashin@oracle.com>
Reviewed-by: default avatarBabu Moger <babu.moger@oracle.com>
Cc: David Miller <davem@davemloft.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent f7fb506f

include/linux/bootmem.h

+1 −0
Original line number Diff line number Diff line
@@ -358,6 +358,7 @@ extern void *alloc_large_system_hash(const char *tablename, 
#define HASH_EARLY	0x00000001	/* Allocating during early boot? */

#define HASH_SMALL	0x00000002	/* sub-page allocation allowed, min

					 * shift passed via *_hash_shift */

#define HASH_ZERO	0x00000004	/* Zero allocated hash table */



/* Only NUMA needs hash distribution. 64bit NUMA architectures have

 * sufficient vmalloc space.

mm/page_alloc.c

+9 −3
Original line number Diff line number Diff line
@@ -7198,6 +7198,7 @@ void *__init alloc_large_system_hash(const char *tablename, 
	unsigned long long max = high_limit;

	unsigned long log2qty, size;

	void *table = NULL;

	gfp_t gfp_flags;



	/* allow the kernel cmdline to have a say */

	if (!numentries) {
@@ -7242,12 +7243,17 @@ void *__init alloc_large_system_hash(const char *tablename, 


	log2qty = ilog2(numentries);



	/*

	 * memblock allocator returns zeroed memory already, so HASH_ZERO is

	 * currently not used when HASH_EARLY is specified.

	 */

	gfp_flags = (flags & HASH_ZERO) ? GFP_ATOMIC | __GFP_ZERO : GFP_ATOMIC;

	do {

		size = bucketsize << log2qty;

		if (flags & HASH_EARLY)

			table = memblock_virt_alloc_nopanic(size, 0);

		else if (hashdist)

			table = __vmalloc(size, GFP_ATOMIC, PAGE_KERNEL);

			table = __vmalloc(size, gfp_flags, PAGE_KERNEL);

		else {

			/*

			 * If bucketsize is not a power-of-two, we may free
@@ -7255,8 +7261,8 @@ void *__init alloc_large_system_hash(const char *tablename, 
			 * alloc_pages_exact() automatically does

			 */

			if (get_order(size) < MAX_ORDER) {

				table = alloc_pages_exact(size, GFP_ATOMIC);

				kmemleak_alloc(table, size, 1, GFP_ATOMIC);

				table = alloc_pages_exact(size, gfp_flags);

				kmemleak_alloc(table, size, 1, gfp_flags);

			}

		}

	} while (!table && size > PAGE_SIZE && --log2qty);

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