linux-kernel - Re: [patch -mm] cpusets: add memory_slab

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: <1236719283.3205.24.camel@calx>
Date:	Tue, 10 Mar 2009 16:08:03 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	David Rientjes <rientjes@...gle.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Paul Menage <menage@...gle.com>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch -mm] cpusets: add memory_slab_hardwall flag

On Tue, 2009-03-10 at 16:50 -0400, Christoph Lameter wrote:
> On Mon, 9 Mar 2009, David Rientjes wrote:
> 
> > On Mon, 9 Mar 2009, Christoph Lameter wrote:
> >
> > > > On large NUMA machines, it is currently possible for a very large
> > > > percentage (if not all) of your slab allocations to come from memory that
> > > > is distant from your application's set of allowable cpus.  Such
> > > > allocations that are long-lived would benefit from having affinity to
> > > > those processors.  Again, this is the typical use case for cpusets: to
> > > > bind memory nodes to groups of cpus with affinity to it for the tasks
> > > > attached to the cpuset.
> > >
> > > Can you show us a real workload that suffers from this issue?
> > >
> >
> > We're more interested in the isolation characteristic, but that also
> > benefits large NUMA machines by keeping nodes free of egregious amounts of
> > slab allocated for remote cpus.
> 
> So no real workload just some isolation idea.
> 
> > > If you want to make sure that an allocation comes from a certain node then
> > > specifying the node in kmalloc_node() will give you what you want.
> > >
> >
> > That's essentially what the change does implicitly: it changes all
> > kmalloc() calls to kmalloc_node() for current->mems_allowed.
> 
> Ok then you can use kmalloc_node?

Yes, he certainly could change every single kmalloc that a process might
ever reach to kmalloc_node. But I don't think that's optimal.

> 
> > > The usage of kernel objects may not be cpuset specific. This is true for
> > > other objects than inode and dentries well.
> > >
> >
> > Yes, and that's why we require the cpuset hardwall on a configurable
> > per-cpuset basis.  If a cpuset has set this option for its workload, then
> > it is demanding object allocations from local memory.  Other cpusets that
> > do not have memory_slab_hardwall set can still allocate from any cpu slab
> > or partial slab, including those allocated for the hardwall cpuset.
> 
> You cannot hardwall something that is used in a shared way by processes in
> multiple cpusets.

He can enforce that every allocation made when a given task is current
conforms. His patch demonstrates that.

-- 
http://selenic.com : development and support for Mercurial and Linux


--
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/