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From: Vlastimil Babka <vbabka@suse.cz>
To: Dan Williams <dan.j.williams@intel.com>, akpm@linux-foundation.org
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
	Michal Hocko <mhocko@suse.com>, Kees Cook <keescook@chromium.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	keith.busch@intel.com
Subject: Re: [PATCH v10 1/3] mm: Shuffle initial free memory to improve memory-side-cache utilization
Date: Fri, 31 May 2019 09:33:36 +0200	[thread overview]
Message-ID: <cddd43de-62f6-6a91-83aa-da02ff17254d@suse.cz> (raw)
In-Reply-To: <154899811738.3165233.12325692939590944259.stgit@dwillia2-desk3.amr.corp.intel.com>

On 2/1/19 6:15 AM, Dan Williams wrote:
> --- a/init/Kconfig
> +++ b/init/Kconfig
> @@ -1714,6 +1714,29 @@ config SLAB_FREELIST_HARDENED
>  	  sacrifies to harden the kernel slab allocator against common
>  	  freelist exploit methods.
>  
> +config SHUFFLE_PAGE_ALLOCATOR
> +	bool "Page allocator randomization"
> +	default SLAB_FREELIST_RANDOM && ACPI_NUMA
> +	help
> +	  Randomization of the page allocator improves the average
> +	  utilization of a direct-mapped memory-side-cache. See section
> +	  5.2.27 Heterogeneous Memory Attribute Table (HMAT) in the ACPI
> +	  6.2a specification for an example of how a platform advertises
> +	  the presence of a memory-side-cache. There are also incidental
> +	  security benefits as it reduces the predictability of page
> +	  allocations to compliment SLAB_FREELIST_RANDOM, but the
> +	  default granularity of shuffling on 4MB (MAX_ORDER) pages is
> +	  selected based on cache utilization benefits.
> +
> +	  While the randomization improves cache utilization it may
> +	  negatively impact workloads on platforms without a cache. For
> +	  this reason, by default, the randomization is enabled only
> +	  after runtime detection of a direct-mapped memory-side-cache.
> +	  Otherwise, the randomization may be force enabled with the
> +	  'page_alloc.shuffle' kernel command line parameter.
> +
> +	  Say Y if unsure.

It says "Say Y if unsure", yet if I run make oldconfig, the default is
N. Does that make sense?

> Page allocator randomization (SHUFFLE_PAGE_ALLOCATOR) [N/y/?] (NEW)


  parent reply	other threads:[~2019-05-31  7:33 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-01  5:15 [PATCH v10 0/3] mm: Randomize free memory Dan Williams
2019-02-01  5:15 ` [PATCH v10 1/3] mm: Shuffle initial free memory to improve memory-side-cache utilization Dan Williams
2019-02-05 22:04   ` Andrew Morton
2019-02-05 23:11     ` Kees Cook
2019-02-05 23:29       ` Matthew Wilcox
2019-05-31  7:33   ` Vlastimil Babka [this message]
2019-05-31 14:59     ` Dan Williams
2019-02-01  5:15 ` [PATCH v10 2/3] mm: Move buddy list manipulations into helpers Dan Williams
2019-02-19 15:24   ` Vlastimil Babka
2019-02-19 17:21     ` Dan Williams
2019-02-01  5:15 ` [PATCH v10 3/3] mm: Maintain randomization of page free lists Dan Williams
2019-02-01  9:58   ` Michal Hocko

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