Messages in this thread |  | | Date | Sat, 5 Apr 2008 10:57:00 -0700 | From | "Paul Menage" <> | Subject | Re: [-mm] Add an owner to the mm_struct (v8) |
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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, 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?
> > >> 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.
Does oprofile show any interesting differences?
Paul
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