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    SubjectRe: [PATCH v3 13/28] slub: create duplicate cache
    On 05/30/2012 12:21 AM, Christoph Lameter wrote:
    > On Wed, 30 May 2012, Glauber Costa wrote:
    >> Well, I'd have to dive in the code a bit more, but that the impression that
    >> the documentation gives me, by saying:
    >> "Cpusets constrain the CPU and Memory placement of tasks to only
    >> the resources within a task's current cpuset."
    >> is that you can't allocate from a node outside that set. Is this correct?
    > Basically yes but there are exceptions (like slab queues etc). Look at the
    > hardwall stuff too that allows more exceptions for kernel allocations to
    > use memory from other nodes.
    >> So extrapolating this to memcg, the situation is as follows:
    >> * You can't use more memory than what you are assigned to.
    >> * In order to do that, you need to account the memory you are using
    >> * and to account the memory you are using, all objects in the page
    >> must belong to you.
    > Cpusets work at the page boundary and they do not have the requirement you
    > are mentioning of all objects in the page having to belong to a certain
    > cpusets. Let that go and things become much easier.
    >> With a predictable enough workload, this is a recipe for working around the
    >> very protection we need to establish: one can DoS a physical box full of
    >> containers, by always allocating in someone else's pages, and pinning kernel
    >> memory down. Never releasing it, so the shrinkers are useless.
    > Sure you can construct hyperthetical cases like that. But then that is
    > true already of other container like logic in the kernel already.
    >> So I still believe that if a page is allocated to a cgroup, all the objects in
    >> there belong to it - unless of course the sharing actually means something -
    >> and identifying this is just too complicated.
    > We have never worked container like logic like that in the kernel due to
    > the complicated logic you would have to put in. The requirement that all
    > objects in a page come from the same container is not necessary. If you
    > drop this notion then things become very easy and the patches will become
    > simple.

    I promise to look at that in more detail and get back to it. In the
    meantime, I think it would be enlightening to hear from other parties as
    well, specially the ones also directly interested in using the technology.

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      Last update: 2012-05-29 23:01    [W:0.029 / U:2.156 seconds]
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