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 10:23:33 -0700 Message-ID: <6599ad830804051023v69caa3d4h6e26ccb420bca899@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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <47F79102.6090406@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 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. > 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. > > 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? How many runs was that over? Ingo's recently posted volanomark tests against -rc7 showed ~3% random variation between runs. Paul