The patch titled
Subject: mm: zero hash tables in allocator
has been added to the -mm tree. Its filename is
mm-zeroing-hash-tables-in-allocator.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-zeroing-hash-tables-in-allocator.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-zeroing-hash-tables-in-allocator.patch
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------------------------------------------------------
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
@@ -7124,6 +7124,7 @@ 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) {
@@ -7168,12 +7169,17 @@ 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
@@ -7181,8 +7187,8 @@ 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);
_
Patches currently in -mm which might be from pasha.tatashin@xxxxxxxxxx are
sparc64-ng4-memset-32-bits-overflow.patch
mm-zeroing-hash-tables-in-allocator.patch
mm-updated-callers-to-use-hash_zero-flag.patch
mm-adaptive-hash-table-scaling.patch
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