[v4 14/15] mm: optimize early system hash allocations

[Pavel Tatashin]

Clients can call alloc_large_system_hash() with flag: HASH_ZERO to specify
that memory that was allocated for system hash needs to be zeroed,
otherwise the memory does not need to be zeroed, and client will initialize
it.

If memory does not need to be zero'd, call the new
memblock_virt_alloc_raw() interface, and thus improve the boot performance.

Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Reviewed-by: Steven Sistare <steven.sistare@xxxxxxxxxx>
Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
Reviewed-by: Bob Picco <bob.picco@xxxxxxxxxx>
---
 mm/page_alloc.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index debea7c0febb..623e2f7634e7 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -7350,18 +7350,17 @@ 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)
+		if (flags & HASH_EARLY) {
+			if (flags & HASH_ZERO)
+				table = memblock_virt_alloc_nopanic(size, 0);
+			else
+				table = memblock_virt_alloc_raw(size, 0);
+		} else if (hashdist) {
 			table = __vmalloc(size, gfp_flags, PAGE_KERNEL);
-		else {
+		} else {
 			/*
 			 * If bucketsize is not a power-of-two, we may free
 			 * some pages at the end of hash table which
-- 
2.13.3