linux-kernel - Re: [PATCH 0/5] make slab gfp fair

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: <1179173129.2942.52.camel@lappy>
Date:	Mon, 14 May 2007 22:05:29 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Matt Mackall <mpm@...enic.com>,
	Christoph Lameter <clameter@....com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Thomas Graf <tgraf@...g.ch>,
	David Miller <davem@...emloft.net>,
	Daniel Phillips <phillips@...gle.com>,
	Pekka Enberg <penberg@...helsinki.fi>
Subject: Re: [PATCH 0/5] make slab gfp fair

On Mon, 2007-05-14 at 12:44 -0700, Andrew Morton wrote:
> On Mon, 14 May 2007 11:12:24 -0500
> Matt Mackall <mpm@...enic.com> wrote:
> 
> > If I understand this correctly:
> > 
> > privileged thread                      unprivileged greedy process
> > kmem_cache_alloc(...)
> >    adds new slab page from lowmem pool
> > do_io()
> >                                        kmem_cache_alloc(...)
> >                                        kmem_cache_alloc(...)
> >                                        kmem_cache_alloc(...)
> >                                        kmem_cache_alloc(...)
> >                                        kmem_cache_alloc(...)
> >                                        ...
> >                                           eats it all
> > kmem_cache_alloc(...) -> ENOMEM
> >    who ate my donuts?!
> 
> Yes, that's my understanding also.
> 
> I can see why it's a problem in theory, but I don't think Peter has yet
> revealed to us why it's a problem in practice.  I got all excited when
> Christoph asked "I am not sure what the point of all of this is.", but
> Peter cunningly avoided answering that ;)
> 
> What observed problem is being fixed here?

I'm moving towards swapping over networked storage. Admittedly a new
feature.

Like with pretty much all other swap solutions; there is the fundamental
vm deadlock: freeing memory requires memory. Current block devices get
around that by using mempools. This works well.

However with network traffic mempools are not easily usable; the network
stack uses kmalloc. By using reserve based allocation we can keep
operating in a similar matter.



-
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/