From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Paul Menage" Subject: Re: [-mm] Add an owner to the mm_struct (v8) Date: Sat, 5 Apr 2008 10:57:00 -0700 Message-ID: <6599ad830804051057n2f2802e4w6179f2e108467494@mail.gmail.com> References: <20080404080544.26313.38199.sendpatchset@localhost.localdomain> <6599ad830804040112q3dd5333aodf6a170c78e61dc8@mail.gmail.com> <47F5E69C.9@linux.vnet.ibm.com> <6599ad830804040150j4946cf92h886bb26000319f3b@mail.gmail.com> <47F5F3FA.7060709@linux.vnet.ibm.com> <6599ad830804041211r37848a6coaa900d8bdac40fbe@mail.gmail.com> <47F79102.6090406@linux.vnet.ibm.com> <6599ad830804051023v69caa3d4h6e26ccb420bca899@mail.gmail.com> <47F7BB69.3000502@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <47F7BB69.3000502@linux.vnet.ibm.com> Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org To: balbir@linux.vnet.ibm.com Cc: Pavel Emelianov , Hugh Dickins , Sudhir Kumar , YAMAMOTO Takashi , lizf@cn.fujitsu.com, linux-kernel@vger.kernel.org, taka@valinux.co.jp, linux-mm@kvack.org, David Rientjes , Andrew Morton , KAMEZAWA Hiroyuki List-Id: linux-mm.kvack.org 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, 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