From: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Subject: 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@xxxxxxxxxx Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx> Reviewed-by: Babu Moger <babu.moger@xxxxxxxxxx> Cc: David Miller <davem@xxxxxxxxxxxxx> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/bootmem.h | 1 + mm/page_alloc.c | 12 +++++++++--- 2 files changed, 10 insertions(+), 3 deletions(-) diff -puN include/linux/bootmem.h~mm-zeroing-hash-tables-in-allocator include/linux/bootmem.h --- a/include/linux/bootmem.h~mm-zeroing-hash-tables-in-allocator +++ a/include/linux/bootmem.h @@ -358,6 +358,7 @@ extern void *alloc_large_system_hash(con #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. diff -puN mm/page_alloc.c~mm-zeroing-hash-tables-in-allocator mm/page_alloc.c --- a/mm/page_alloc.c~mm-zeroing-hash-tables-in-allocator +++ a/mm/page_alloc.c @@ -7198,6 +7198,7 @@ void *__init alloc_large_system_hash(con 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(con 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(con * 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); _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
