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Date: Sun, 06 Apr 2008 00:29:20 +0530 From: Balbir Singh <balbir@...ux.vnet.ibm.com> To: Paul Menage <menage@...gle.com> CC: Pavel Emelianov <xemul@...nvz.org>, Hugh Dickins <hugh@...itas.com>, Sudhir Kumar <skumar@...ux.vnet.ibm.com>, YAMAMOTO Takashi <yamamoto@...inux.co.jp>, lizf@...fujitsu.com, linux-kernel@...r.kernel.org, taka@...inux.co.jp, linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>, Andrew Morton <akpm@...ux-foundation.org>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> Subject: Re: [-mm] Add an owner to the mm_struct (v8) Paul Menage wrote: > On Sat, Apr 5, 2008 at 10:48 AM, Balbir Singh <balbir@...ux.vnet.ibm.com> wrote: >> Paul Menage wrote: >> > On Sat, Apr 5, 2008 at 7:47 AM, Balbir Singh <balbir@...ux.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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