Messages in this thread |  | | Date | Sun, 06 Apr 2008 00:29:20 +0530 | From | Balbir Singh <> | Subject | Re: [-mm] Add an owner to the mm_struct (v8) |
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Paul Menage wrote: > On Sat, Apr 5, 2008 at 10:48 AM, Balbir Singh <balbir@linux.vnet.ibm.com> wrote: >> Paul Menage wrote: >> > On Sat, Apr 5, 2008 at 7:47 AM, Balbir Singh <balbir@linux.vnet.ibm.com> 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 IBM, ISTL
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