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: <20080220131515.GF11364@sgi.com>
Date:	Wed, 20 Feb 2008 07:15:15 -0600
From:	Robin Holt <holt@....com>
To:	Andrea Arcangeli <andrea@...ranet.com>
Cc:	Robin Holt <holt@....com>, Nick Piggin <npiggin@...e.de>,
	akpm@...ux-foundation.org, Avi Kivity <avi@...ranet.com>,
	Izik Eidus <izike@...ranet.com>,
	kvm-devel@...ts.sourceforge.net,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	general@...ts.openfabrics.org,
	Steve Wise <swise@...ngridcomputing.com>,
	Roland Dreier <rdreier@...co.com>,
	Kanoj Sarcar <kanojsarcar@...oo.com>, steiner@....com,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	daniel.blueman@...drics.com, Christoph Lameter <clameter@....com>
Subject: Re: [PATCH] mmu notifiers #v6

On Wed, Feb 20, 2008 at 01:32:36PM +0100, Andrea Arcangeli wrote:
> On Wed, Feb 20, 2008 at 06:24:24AM -0600, Robin Holt wrote:
> > We do not need to do any allocation in the messaging layer, all
> > structures used for messaging are allocated at module load time.
> > The allocation discussions we had early on were about trying to
> > rearrange you notifiers to allow a seperate worker thread to do the
> > invalidate and then the main thread would spin waiting for the worker to
> > complete.  That was canned by the moving your notifier to before the
> > lock was grabbed which led us to the point of needing a _begin and _end.
> 
> I thought you called some net/* function inside the mmu notifier
> methods. Those always require several ram allocations internally.

Nope, that was the discussions with the IB folks.  We only use XPC and
both the messages we send and the XPC internals do not need to allocate.

> > So, fundamentally, how would they be different?  Would we be required to
> > add another notifier list to the mm and have two seperate callout
> > points?  Reduction would end up with the same half-registered
> > half-not-registered situation you point out above.  Then further
> > reduction would lead to the elimination of the callouts you have just
> > proposed and using the _begin/_end callouts and we are back to
> > Christoph's current patch.
> 
> Did you miss Nick's argument that we'd need to change some VM lock to
> mutex and solve lock issues first? Are you implying mutex are more
> efficient for the VM? (you may seek support from preempt-rt folks at
> least) or are you implying the VM would better run slower with mutex
> in order to have a single config option?

That would be if we needed to support file backed mappings and hugetlbfs
mappings.  Currently (and for the last 6 years), XPMEM has not supported
either of those.  I don't view either as being a realistic possibility,
but it is certainly something we would need to address before either
could be supported.

Robin
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ