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Date: Sat, 05 Apr 2008 23:18:25 +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 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? >> If the user is unable to remove a cgroup node, it will >> be due a valid reason, the group_leader is still around, since the threads are >> still around. The user in that case should wait for notify_on_release. >> >> > >> > To me, it seems that setting up a *virtual address space* cgroup >> > hierarchy and then putting half your threads in one group and half in >> > the another is asking for trouble. We need to not break in that >> > situation, but I'm not sure it's a case to optimize for. >> >> That could potentially happen, if the virtual address space cgroup and cpu >> control cgroup were bound together in the same hierarchy by the sysadmin. > > 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. >> 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. > How many runs was that over? Ingo's recently posted volanomark tests > against -rc7 showed ~3% random variation between runs. I ran the test four times. I took the average of runs, I did see some variation between runs, I did not calculate the standard deviation. -- 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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