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    SubjectRe: [-mm] Add an owner to the mm_struct (v8)
    Paul Menage wrote:
    > On Sat, Apr 5, 2008 at 10:48 AM, Balbir Singh <> wrote:
    >> Paul Menage wrote:
    >> > On Sat, Apr 5, 2008 at 7:47 AM, Balbir Singh <> wrote:
    >> >> Repeating my question earlier
    >> >>
    >> >> Can we delay setting task->cgroups = &init_css_set for the group_leader, until
    >> >> all threads have exited?
    >> >
    >> > Potentially, yes. It also might make more sense to move the
    >> > exit_cgroup() for all threads to a later point rather than special
    >> > case delayed group leaders.
    >> >
    >> Yes, that makes sense. I think that patch should be independent of this one
    >> though? What do you think?
    > Yes, it would probably need to be a separate patch. The current
    > positioning of cgroup_exit() is more or less inherited from cpusets.
    > I'd need to figure out if a change like that would break anything.

    Yes, thats understandable

    >> >
    >> > Yes, I agree it could potentially happen. But it seems like a strange
    >> > thing to do if you're planning to be not have the same groupings for
    >> > cpu and va.
    >> It's easier to set it up that way. Usually the end user gets the same SLA for
    >> memory, CPU and other resources, so it makes sense to bind the controllers together.
    > True - but in that case why wouldn't they have the same SLA for
    > virtual address space too?

    Yes, mostly. That's why I had made the virtual address space patches as a config
    option on top of the memory controller :)

    >> >> I measured the overhead of removing the delay_group_leader optimization and
    >> >> found a 4% impact on throughput (with volanomark, that is one of the
    >> >> multi-threaded benchmarks I know of).
    >> >
    >> > Interesting, I thought (although I've never actually looked at the
    >> > code) that volanomark was more of a scheduling benchmark than a
    >> > process start/exit benchmark. How frequently does it have processes
    >> > (not threads) exiting?
    >> >
    >> I could not find any other interesting benchmark for benchmarking fork/exits. I
    >> know that volanomark is heavily threaded, so I used it. The threads quickly exit
    >> after processing the messages, I thought that would be a good test to see the
    >> overhead.
    > But surely the performance of thread exits wouldn't be affected by the
    > delay_group_leader(p) change, since none of the exiting threads would
    > be a group leader. That optimization only matters when the entire
    > process exits.

    On the client side, each JVM instance exits after the test. I see the thread
    group leader exit as well through getdelays (I see TGID exits).

    > Does oprofile show any interesting differences?

    Need to try oprofile.

    Warm Regards,
    Balbir Singh
    Linux Technology Center

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