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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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