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[195.135.220.15]) by mx.google.com with ESMTPS id w12si3434564edt.193.2019.05.31.00.33.38 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 31 May 2019 00:33:38 -0700 (PDT) Received-SPF: pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=pass (google.com: domain of vbabka@suse.cz designates 195.135.220.15 as permitted sender) smtp.mailfrom=vbabka@suse.cz X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 9F973AE0E; Fri, 31 May 2019 07:33:37 +0000 (UTC) Subject: Re: [PATCH v10 1/3] mm: Shuffle initial free memory to improve memory-side-cache utilization To: Dan Williams , akpm@linux-foundation.org Cc: Dave Hansen , Michal Hocko , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org, keith.busch@intel.com References: <154899811208.3165233.17623209031065121886.stgit@dwillia2-desk3.amr.corp.intel.com> <154899811738.3165233.12325692939590944259.stgit@dwillia2-desk3.amr.corp.intel.com> From: Vlastimil Babka Openpgp: preference=signencrypt Autocrypt: addr=vbabka@suse.cz; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <154899811738.3165233.12325692939590944259.stgit@dwillia2-desk3.amr.corp.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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)