linux-kernel - Re: [patch] mm: pageable memory allocator (for DRM-GEM?)

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]

Date:	Thu, 25 Sep 2008 04:30:14 +0200
From:	Nick Piggin <npiggin@...e.de>
To:	Keith Packard <keithp@...thp.com>
Cc:	eric@...olt.net, hugh@...itas.com, hch@...radead.org,
	airlied@...ux.ie, jbarnes@...tuousgeek.org,
	thomas@...gstengraphics.com, dri-devel@...ts.sourceforge.net,
	Linux Memory Management List <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [patch] mm: pageable memory allocator (for DRM-GEM?)

On Wed, Sep 24, 2008 at 06:20:22PM -0700, Keith Packard wrote:
> On Thu, 2008-09-25 at 02:30 +0200, Nick Piggin wrote:
> 
> > I guess so. A big problem of ioctls is just that they had been easier to
> > add so they got less thought and review ;) If your ioctls are stable,
> > correct, cross platform etc. then I guess that's the best you can do.
> 
> One does what one can. Of course, in this case, 'cross platform' is just
> x86/x86_64 as we're talking Intel integrated graphics. When (if?) we
> figure out how to create a common interface across multiple cards for
> some of these operations, we'll probably discover mistakes. We have
> tried to be careful, but we cannot test in any other environment.

OK, that's all that can be asked I guess. Low level object / memory 
management hopefully can be shared.

 
> > Well, no not a seperate filesystem to do the pageable backing store, but
> > a filesystem to do your object management. If there was a need for pageable
> > RAM backing store, then you would still go back to the pageable allocator. 
> 
> Now that you've written one, we could go back and think about building a
> file system and using fds for our operations. It would be a whole lot
> easier than starting from scratch.

If it helps open some other possibilities, then great.

 
> > You can map them to userspace if you just take a page at a time and insert
> > them into the page tables at fault time (or mmap time if you prefer).
> > Currently, this will mean that mmapped pages would not be swappable; is
> > that a problem?
> 
> Yes. We leave a lot of objects mapped to user space as mmap isn't
> exactly cheap. We're trying to use pread/pwrite for as much bulk I/O as
> we can, but at this point, we're still mapping most of the pages we
> allocate into user space and leaving them. Things like textures and
> render buffers will get mmapped if there are any software fallbacks.
> Other objects, like vertex buffers, will almost always end up mapped.
> 
> One of our explicit design goals was to make sure user space couldn't
> ever pin arbitrary amounts of memory; I'd hate to go back on that as it
> seems like an important property for any subsystem designed to support
> regular user applications in a general purpose desktop environment. I
> don't want to trust user space to do the right thing, I want to enforce
> that from kernel space.

OK. I will have to add some facilities to allow mmaps that go back through
to tmpfs and be swappable... Thanks for the data point.
--
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/