Messages in this thread | | | Date | Mon, 28 Feb 2005 00:20:40 +0900 | From | KaiGai Kohei <> | Subject | Re: [Lse-tech] Re: A common layer for Accounting packages |
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Hi,
>>Kaigai Kohei <kaigai@ak.jp.nec.com> wrote: >> >>>In my understanding, what Andrew Morton said is "If target functionality can >>> implement in user space only, then we should not modify the kernel-tree". >> >>fork, exec and exit upcalls sound pretty good to me. As long as >> >>a) they use the same common machinery and >> >>b) they are next-to-zero cost if something is listening on the netlink >> socket but no accounting daemon is running. > > > b) would involved being able to avoid sending netlink messages in case there are > no listeners. AFAIK that isnt possible currently, netlink sends > packets unconditionally. > > Am I wrong?
In current implementaion, you might be right. But we should make an effort to achieve the requirement-(b) from now.
And, why can't netlink packets send always? If there are fork/exec/exit hooks, and they call CSA or other process-grouping modules, then those modules will decide whether packets for interaction with the daemon should be sent or not. In most considerable case, CSA's kernel-loadable-module using such hooks will not be loaded when no accounting daemon is running. Adversely, this module must be loaded when accounting daemon needs CSA's netlink packets. Thus, it is only necessary to refer flag valiable and to execute conditional-jump when no-accounting daemon is running.
In my estimation, we must pay additional cost for an increment-operation, an decrement-op, an comparison-op and an conditional jump-op. It's enough lightweight, I think.
For example: If CSA's module isn't loaded, 'privates_for_grouping' will be empty.
inline int on_fork_hook(task_struct *parent, task_struct *newtask){ rcu_read_lock(); if( !list_empty(&parent->privates_for_grouping) ){ ..<Calling to any process grouping module>..; } rcu_read_unlock(); }
Thanks, -- Linux Promotion Center, NEC KaiGai Kohei <kaigai@ak.jp.nec.com> - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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