From: Dan Williams <dan.j.williams@intel.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
Michal Hocko <mhocko@suse.com>,
Kees Cook <keescook@chromium.org>, Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Keith Busch <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 07:59:28 -0700 [thread overview]
Message-ID: <CAPcyv4g-g=Gyf0T1rENCEH_2KyLtt74kiLydxO=__tM71_bYww@mail.gmail.com> (raw)
In-Reply-To: <cddd43de-62f6-6a91-83aa-da02ff17254d@suse.cz>
On Fri, May 31, 2019 at 12:33 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>
> 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?
The default is due to the general policy of not forcing users into new
kernel functionality (i.e. the common Linus objection when a new
config symbol is default 'y') . However, if someone is actively
considering whether to enable it I think there's no harm in
recommending 'y' because the facility currently needs to be paired
with the page_alloc.shuffle=1 command line option.
next prev parent reply other threads:[~2019-05-31 14:59 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
2019-05-31 14:59 ` Dan Williams [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CAPcyv4g-g=Gyf0T1rENCEH_2KyLtt74kiLydxO=__tM71_bYww@mail.gmail.com' \
--to=dan.j.williams@intel.com \
--cc=akpm@linux-foundation.org \
--cc=dave.hansen@linux.intel.com \
--cc=keescook@chromium.org \
--cc=keith.busch@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mhocko@suse.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).