linux-kernel - [tip:x86/mm] x86: mm: Use 2GB memory block size on large-memory x86-64 systems

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Date:	Tue, 4 Nov 2014 09:22:29 -0800
From:	tip-bot for Daniel J Blueman <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	sp@...ascale.com, tglx@...utronix.de, hpa@...or.com,
	linux-kernel@...r.kernel.org, bhelgaas@...gle.com,
	daniel@...ascale.com, mingo@...nel.org
Subject: [tip:x86/mm] x86: mm:
  Use 2GB memory block size on large-memory x86-64 systems

Commit-ID:  bdee237c0343a5d1a6cf72c7ea68e88338b26e08
Gitweb:     http://git.kernel.org/tip/bdee237c0343a5d1a6cf72c7ea68e88338b26e08
Author:     Daniel J Blueman <daniel@...ascale.com>
AuthorDate: Tue, 4 Nov 2014 16:29:44 +0800
Committer:  Thomas Gleixner <tglx@...utronix.de>
CommitDate: Tue, 4 Nov 2014 18:19:27 +0100

x86: mm: Use 2GB memory block size on large-memory x86-64 systems

On large-memory x86-64 systems of 64GB or more with memory hot-plug
enabled, use a 2GB memory block size. Eg with 64GB memory, this reduces
the number of directories in /sys/devices/system/memory from 512 to 32,
making it more manageable, and reducing the creation time accordingly.

This caveat is that the memory can't be offlined (for hotplug or
otherwise) with the finer default 128MB granularity, but this is
unimportant due to the high memory densities generally used with such
large-memory systems, where eg a single DIMM is the order of 16GB.

Signed-off-by: Daniel J Blueman <daniel@...ascale.com>
Cc: Steffen Persvold <sp@...ascale.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>
Link: http://lkml.kernel.org/r/1415089784-28779-4-git-send-email-daniel@numascale.com
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/mm/init_64.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 4cb8763..ebca30f 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -52,7 +52,6 @@
 #include <asm/numa.h>
 #include <asm/cacheflush.h>
 #include <asm/init.h>
-#include <asm/uv/uv.h>
 #include <asm/setup.h>
 
 #include "mm_internal.h"
@@ -1247,12 +1246,10 @@ static unsigned long probe_memory_block_size(void)
 	/* start from 2g */
 	unsigned long bz = 1UL<<31;
 
-#ifdef CONFIG_X86_UV
-	if (is_uv_system()) {
-		printk(KERN_INFO "UV: memory block size 2GB\n");
+	if (totalram_pages >= (64ULL << (30 - PAGE_SHIFT))) {
+		pr_info("Using 2GB memory block size for large-memory system\n");
 		return 2UL * 1024 * 1024 * 1024;
 	}
-#endif
 
 	/* less than 64g installed */
 	if ((max_pfn << PAGE_SHIFT) < (16UL << 32))
--
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