Re: [PATCH v2 5/5] Numachip: use 2GB memory block size

From: Ingo Molnar
Date: Sun Oct 19 2014 - 05:23:52 EST



* Daniel J Blueman <daniel@xxxxxxxxxxxxx> wrote:

> Use appropriate memory block size to reduce sysfs entry creation time
> by 16x.
>
> Boot-tested with the four permutations of X86_UV and X86_NUMACHIP.
>
> Signed-off-by: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
> ---
> arch/x86/mm/init_64.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
> index 5621c47..22ea6de 100644
> --- a/arch/x86/mm/init_64.c
> +++ b/arch/x86/mm/init_64.c
> @@ -53,6 +53,7 @@
> #include <asm/cacheflush.h>
> #include <asm/init.h>
> #include <asm/uv/uv.h>
> +#include <asm/numachip/numachip.h>
> #include <asm/setup.h>
>
> #include "mm_internal.h"
> @@ -1235,9 +1236,9 @@ 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");
> +#ifdef CONFIG_X86_64
> + if (is_uv_system() || is_numachip_system()) {
> + pr_info("Memory block size 2GB for large-SMP system\n");
> return 2UL * 1024 * 1024 * 1024;

It would be a lot cleaner and more robust to have a more
intelligent decision here.

Is there a reliable indicator for large 'sysfs entry creation
time', such as a lot of RAM present?

Also, it would be nice to list the pros/cons of this change, an
advantage is reduced overhead - what are the disadvantages?

Thanks,

Ingo
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