linux-kernel - Re: [PATCH 29/33] autonuma: page

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20121004183819.GM25675@redhat.com>
Date:	Thu, 4 Oct 2012 20:38:19 +0200
From:	Andrea Arcangeli <aarcange@...hat.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <pzijlstr@...hat.com>,
	Ingo Molnar <mingo@...e.hu>, Mel Gorman <mel@....ul.ie>,
	Hugh Dickins <hughd@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Hillf Danton <dhillf@...il.com>,
	Andrew Jones <drjones@...hat.com>,
	Dan Smith <danms@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Paul Turner <pjt@...gle.com>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Mike Galbraith <efault@....de>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: Re: [PATCH 29/33] autonuma: page_autonuma

Hi Christoph,

On Thu, Oct 04, 2012 at 06:17:37PM +0000, Christoph Lameter wrote:
> On Thu, 4 Oct 2012, Andrea Arcangeli wrote:
> 
> > So we could drop page_autonuma by creating a CONFIG_SLUB=y dependency
> > (AUTONUMA wouldn't be available in the kernel config if SLAB=y, and it
> > also wouldn't be available on 32bit archs but the latter isn't a
> > problem).
> 
> Nope it should depend on page struct alignment. Other kernel subsystems
> may be depeding on page struct alignment in the future (and some other
> arches may already have that requirement)

But currently only SLUB x86 64bit selects
CONFIG_HAVE_ALIGNED_STRUCT_PAGE:

arch/Kconfig:config HAVE_ALIGNED_STRUCT_PAGE
arch/x86/Kconfig:       select HAVE_ALIGNED_STRUCT_PAGE if SLUB && !M386
include/linux/mm_types.h:       defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
include/linux/mm_types.h:#ifdef CONFIG_HAVE_ALIGNED_STRUCT_PAGE
mm/slub.c:    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
mm/slub.c:    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
mm/slub.c:    defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)

So in practice a dependency on CONFIG_HAVE_ALIGNED_STRUCT_PAGE would
still mean the same: only available when SLUB enables it, and only on
x86 64bit (ppc64?).

If you mean CONFIG_AUTONUMA=y should select (not depend) on
CONFIG_HAVE_ALIGNED_STRUCT_PAGE, that would allow to enable it in all
.configs but it would have a worse cons: losing 8bytes per page
unconditionally (even when booting on non-NUMA hardware).

The current page_autonuma solution is substantially memory-cheaper
than selecting CONFIG_HAVE_ALIGNED_STRUCT_PAGE: it allocates 2bytes
per page at boot time but only if booting on real NUMA hardware
(without altering the page structure). So to me it looks still quite a
decent tradeoff.

Thanks,
Andrea
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/