Commit bdee237c authored Nov 04, 2014 by Daniel J Blueman Committed by Thomas Gleixner Nov 04, 2014

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@numascale.com>
Cc: Steffen Persvold <sp@numascale.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Link: http://lkml.kernel.org/r/1415089784-28779-4-git-send-email-daniel@numascale.com

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

parent 63e7b6d9

arch/x86/mm/init_64.c

+2 −5

Original line number	Diff line number	Diff line
		@@ -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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