From mboxrd@z Thu Jan 1 00:00:00 1970 From: Balbir Singh Subject: Re: [-mm] Add an owner to the mm_struct (v8) Date: Sun, 06 Apr 2008 00:29:20 +0530 Message-ID: <47F7CC08.4090209@linux.vnet.ibm.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> <6599ad830804051057n2f2802e4w6179f2e108467494@mail.gmail.com> Reply-To: balbir@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: <6599ad830804051057n2f2802e4w6179f2e108467494@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org To: Paul Menage 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 Paul Menage wrote: > 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, 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