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

Cedric Le Goater
2007-07-09T20:25:50Z

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@openvz.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;
> +};
> +
> 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 ?

thanks,

C.