linux-kernel - Re: [PATCH 4/16] Change data structures for pid namespaces

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Message-ID: <46932F69.8020101@openvz.org>
Date:	Tue, 10 Jul 2007 11:04:09 +0400
From:	Pavel Emelianov <xemul@...nvz.org>
To:	sukadev@...ibm.com
CC:	Cedric Le Goater <clg@...ibm.com>, Andrew Morton <akpm@...l.org>,
	Serge Hallyn <serue@...ibm.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Linux Containers <containers@...ts.osdl.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kirill Korotaev <dev@...nvz.org>
Subject: Re: [PATCH 4/16] Change data structures for pid namespaces

sukadev@...ibm.com wrote:
> Cedric Le Goater [clg@...ibm.com] wrote:
> | Pavel Emelianov wrote:
> | > struct pid_namespace will have the kmem_cache to allocate
> | > the pids from, the parent, as they are hierarchical, and
> | > the level of nesting value.
> | > 
> | > struct pid will have a variable length array of pid_number-s
> | > one for each namespace this pid lives in. The level value
> | > shows the level of the namespace this pid lives in and thus -
> | > the number of elements in the numbers array.
> | > 
> | > Signed-off-by: Pavel Emelianov <xemul@...nvz.org>
> | > 
> | > ---
> | > 
> | >  include/linux/init_task.h     |    6 ++++++
> | >  include/linux/pid.h           |    9 +++++++++
> | >  include/linux/pid_namespace.h |    3 +++
> | >  kernel/pid.c                  |    3 ++-
> | >  4 files changed, 20 insertions(+), 1 deletion(-)
> | > 
> | > diff -upr linux-2.6.22-rc4-mm2.orig/include/linux/pid.h linux-2.6.22-rc4-mm2-2/include/linux/pid.h
> | > --- linux-2.6.22-rc4-mm2.orig/include/linux/pid.h	2007-06-14 12:14:29.000000000 +0400
> | > +++ linux-2.6.22-rc4-mm2-2/include/linux/pid.h	2007-07-04 19:00:38.000000000 +0400
> | > @@ -40,6 +40,13 @@ enum pid_type
> | >   * processes.
> | >   */
> | > 
> | > +struct pid_number {
> | > +	/* Try to keep pid_chain in the same cacheline as nr for find_pid */
> | > +	int nr;
> | > +	struct pid_namespace *ns;
> | > +	struct hlist_node pid_chain;
> | > +};
> 
> We meant to go back and look at removing the extra 'struct pid *' we had
> here. Looks like you did that. Cool.
> 
> | > +
> | >  struct pid
> | >  {
> | >  	atomic_t count;
> | > @@ -40,6 +40,8 @@ enum pid_type
> | >  	/* lists of tasks that use this pid */
> | >  	struct hlist_head tasks[PIDTYPE_MAX];
> | >  	struct rcu_head rcu;
> | > +	int level;
> | > +	struct pid_number numbers[1];
> | >  };
> | > 
> | >  extern struct pid init_struct_pid;
> | > diff -upr linux-2.6.22-rc4-mm2.orig/include/linux/pid_namespace.h linux-2.6.22-rc4-mm2-2/include/linux/pid_namespace.h
> | > --- linux-2.6.22-rc4-mm2.orig/include/linux/pid_namespace.h	2007-06-14 12:14:29.000000000 +0400
> | > +++ linux-2.6.22-rc4-mm2-2/include/linux/pid_namespace.h	2007-07-04 19:00:39.000000000 +0400
> | > @@ -16,7 +15,10 @@ struct pidmap {
> | >  	struct kref kref;
> | >  	struct pidmap pidmap[PIDMAP_ENTRIES];
> | >  	int last_pid;
> | > +	int level;
> | >  	struct task_struct *child_reaper;
> | > +	struct kmem_cache *pid_cachep;
> | 
> | so, that looks like a good idea to have the cache in the pidmap. could you 
> | push that independently to see how it all fits together ?
> 
> Yes. I like this idea too.

OK. I will collect the patches you Acked and send them to Andrew independently.

> | 
> | thanks,
> | 
> | C.
> 

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