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: Sat, 05 Apr 2008 23:18:25 +0530 Message-ID: <47F7BB69.3000502@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> 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: <6599ad830804051023v69caa3d4h6e26ccb420bca899@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 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? >> 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