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    SubjectRe: [PATCH 4/16] Change data structures for pid namespaces
    Cedric Le Goater [clg@fr.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@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;
    | > +};

    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.

    |
    | thanks,
    |
    | C.
    -
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