lkml.org 
[lkml]   [2011]   [Mar]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC 0/3] Implementation of cgroup isolation
    On Tue 29-03-11 21:15:59, Zhu Yanhai wrote:
    > Michal,

    Hi,

    > Maybe what we need here is some kind of trade-off?
    > Let's say a new configuable parameter reserve_limit, for the cgroups
    > which want to
    > have some guarantee in the memory resource, we have:
    >
    > limit_in_bytes > soft_limit > reserve_limit
    >
    > MEM[limit_in_bytes..soft_limit] are the bytes that I'm willing to contribute
    > to the others if they are short of memory.
    >
    > MEM[soft_limit..reserve_limit] are the bytes that I can afford if the others
    > are still eager for memory after I gave them MEM[limit_in_bytes..soft_limit].
    >
    > MEM[reserve_limit..0] are the bytes which is a must for me to guarantee QoS.
    > Nobody is allowed to steal them.
    >
    > And reserve_limit is 0 by default for the cgroups who don't care about Qos.
    >
    > Then the reclaim path also needs some changes, i.e, balance_pgdat():
    > 1) call mem_cgroup_soft_limit_reclaim(), if nr_reclaimed is meet, goto finish.
    > 2) shrink the global LRU list, and skip the pages which belong to the cgroup
    > who have set a reserve_limit. if nr_reclaimed is meet, goto finish.

    Isn't this an overhead that would slow the whole thing down. Consider
    that you would need to lookup page_cgroup for every page and touch
    mem_cgroup to get the limit.
    The point of the isolation is to not touch the global reclaim path at
    all.

    > 3) shrink the cgroups who have set a reserve_limit, and leave them with only
    > the reserve_limit bytes they need. if nr_reclaimed is meet, goto finish.
    > 4) OOM
    >
    > Does it make sense?

    It sounds like a good thing - in that regard it is more generic than
    a simple flag - but I am afraid that the implementation wouldn't be
    that easy to preserve the performance and keep the balance between
    groups. But maybe it can be done without too much cost.

    Thanks
    --
    Michal Hocko
    SUSE Labs
    SUSE LINUX s.r.o.
    Lihovarska 1060/12
    190 00 Praha 9
    Czech Republic


    \
     
     \ /
      Last update: 2011-03-29 15:45    [W:0.030 / U:0.588 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site