linux-kernel - [PATCH 05/19] arm64: get rid of superfluous __GFP

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Date:	Mon, 11 Apr 2016 13:07:58 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	<linux-mm@...ck.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Michal Hocko <mhocko@...e.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will.deacon@....com>, linux-arch@...r.kernel.org
Subject: [PATCH 05/19] arm64: get rid of superfluous __GFP_REPEAT

From: Michal Hocko <mhocko@...e.com>

__GFP_REPEAT has a rather weak semantic but since it has been introduced
around 2.6.12 it has been ignored for low order allocations.

{pte,pmd,pud}_alloc_one{_kernel}, late_pgtable_alloc use PGALLOC_GFP for
__get_free_page (aka order-0).

pgd_alloc is slightly more complex because it allocates from pgd_cache
if PGD_SIZE != PAGE_SIZE and PGD_SIZE depends on the configuration
(CONFIG_ARM64_VA_BITS, PAGE_SHIFT and CONFIG_PGTABLE_LEVELS).

As per
config PGTABLE_LEVELS
	int
	default 2 if ARM64_16K_PAGES && ARM64_VA_BITS_36
	default 2 if ARM64_64K_PAGES && ARM64_VA_BITS_42
	default 3 if ARM64_64K_PAGES && ARM64_VA_BITS_48
	default 3 if ARM64_4K_PAGES && ARM64_VA_BITS_39
	default 3 if ARM64_16K_PAGES && ARM64_VA_BITS_47
	default 4 if !ARM64_64K_PAGES && ARM64_VA_BITS_48

we should have the following options

CONFIG_ARM64_VA_BITS:48 CONFIG_PGTABLE_LEVELS:4 PAGE_SIZE:4k size:4096 pages:1
CONFIG_ARM64_VA_BITS:48 CONFIG_PGTABLE_LEVELS:4 PAGE_SIZE:16k size:16 pages:1
CONFIG_ARM64_VA_BITS:48 CONFIG_PGTABLE_LEVELS:3 PAGE_SIZE:64k size:512 pages:1
CONFIG_ARM64_VA_BITS:47 CONFIG_PGTABLE_LEVELS:3 PAGE_SIZE:16k size:16384 pages:1
CONFIG_ARM64_VA_BITS:42 CONFIG_PGTABLE_LEVELS:2 PAGE_SIZE:64k size:65536 pages:1
CONFIG_ARM64_VA_BITS:39 CONFIG_PGTABLE_LEVELS:3 PAGE_SIZE:4k size:4096 pages:1
CONFIG_ARM64_VA_BITS:36 CONFIG_PGTABLE_LEVELS:2 PAGE_SIZE:16k size:16384 pages:1

All of them fit into a single page (aka order-0). This means that this
flag has never been actually useful here because it has always been used
only for PAGE_ALLOC_COSTLY requests.

Cc: Catalin Marinas <catalin.marinas@....com>
Cc: Will Deacon <will.deacon@....com>
Cc: linux-arch@...r.kernel.org
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 arch/arm64/include/asm/pgalloc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
index ff98585d085a..d25f4f137c2a 100644
--- a/arch/arm64/include/asm/pgalloc.h
+++ b/arch/arm64/include/asm/pgalloc.h
@@ -26,7 +26,7 @@
 
 #define check_pgt_cache()		do { } while (0)
 
-#define PGALLOC_GFP	(GFP_KERNEL | __GFP_NOTRACK | __GFP_REPEAT | __GFP_ZERO)
+#define PGALLOC_GFP	(GFP_KERNEL | __GFP_NOTRACK | __GFP_ZERO)
 #define PGD_SIZE	(PTRS_PER_PGD * sizeof(pgd_t))
 
 #if CONFIG_PGTABLE_LEVELS > 2
-- 
2.8.0.rc3