netdev - Re: [RFC PATCH 2/2] PID-based packet filtering support

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Date:	Thu, 5 Apr 2012 12:29:44 -0400
From:	chetan loke <loke.chetan@...il.com>
To:	Nuno Martins <nuno.martins@...xamagica.pt>
Cc:	netdev <netdev@...r.kernel.org>,
	Alfredo Matos <alfredo.matos@...xamagica.pt>,
	Paulo Trezentos <paulo.trezentos@...xamagica.pt>
Subject: Re: [RFC PATCH 2/2] PID-based packet filtering support

On Thu, Apr 5, 2012 at 5:41 AM, Nuno Martins
<nuno.martins@...xamagica.pt> wrote:
> Our tests with 1024 node tree gives us something like 1.3 us on
> average. Your suggestion makes a lot of sense, and we will definitely
> look into.
> This doesn't seem hard to do as we are considering introducing a pid
> based hash table, with a tree in each entry, which can and possibly
> should be pre-allocated.

Also as a defensive mechanism(and if not present already) it may not
be a bad idea to add the following check whenever you are adding or
deleting a node:

if (pidmonitor->curr_num_monitored_pid_nodes >
pidmax_or_whichever_runtime_max_scheduler_uses) {
   WARN_ONCE(....);
    delete_all_nodes_from_the_tree(); // including the current one -
if you were in the middle of a new insert.
    // This way at least your monitoring tool might pick this up and
the user/sysadmin might dig into it.
}

Note: pidmonitor is some global struct and
curr_num_monitored_pid_nodes == number of pids you are currently
monitoring.

By adding this minimal code, if there are any stray nodes in the
tree(over a period of time) because of a bug in the clean up logic
then we might be able to detect it.


> Nuno Martins

Chetan
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