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    Subject[RFC][PATCH v2 2/7] Scaling msgmni to the number of ipc namespaces
    [PATCH 02/07]

    Since all the namespaces see the same amount of memory (the total one)
    this patch introduces a new variable that counts the ipc namespaces and
    divides msg_ctlmni by this counter.

    Signed-off-by: Nadia Derbey <Nadia.Derbey@bull.net>

    ---
    include/linux/ipc.h | 1 +
    ipc/msg.c | 10 +++++++---
    ipc/util.c | 7 +++++++
    3 files changed, 15 insertions(+), 3 deletions(-)

    Index: linux-2.6.24/include/linux/ipc.h
    ===================================================================
    --- linux-2.6.24.orig/include/linux/ipc.h 2008-01-29 16:54:38.000000000 +0100
    +++ linux-2.6.24/include/linux/ipc.h 2008-01-31 10:03:47.000000000 +0100
    @@ -121,6 +121,7 @@ struct ipc_namespace {
    };

    extern struct ipc_namespace init_ipc_ns;
    +extern atomic_t nr_ipc_ns;

    #ifdef CONFIG_SYSVIPC
    #define INIT_IPC_NS(ns) .ns = &init_ipc_ns,
    Index: linux-2.6.24/ipc/util.c
    ===================================================================
    --- linux-2.6.24.orig/ipc/util.c 2008-01-29 16:55:04.000000000 +0100
    +++ linux-2.6.24/ipc/util.c 2008-01-31 10:05:58.000000000 +0100
    @@ -51,6 +51,9 @@ struct ipc_namespace init_ipc_ns = {
    },
    };

    +atomic_t nr_ipc_ns = ATOMIC_INIT(1);
    +
    +
    static struct ipc_namespace *clone_ipc_ns(struct ipc_namespace *old_ns)
    {
    int err;
    @@ -61,6 +64,8 @@ static struct ipc_namespace *clone_ipc_n
    if (ns == NULL)
    goto err_mem;

    + atomic_inc(&nr_ipc_ns);
    +
    err = sem_init_ns(ns);
    if (err)
    goto err_sem;
    @@ -80,6 +85,7 @@ err_msg:
    sem_exit_ns(ns);
    err_sem:
    kfree(ns);
    + atomic_dec(&nr_ipc_ns);
    err_mem:
    return ERR_PTR(err);
    }
    @@ -109,6 +115,7 @@ void free_ipc_ns(struct kref *kref)
    msg_exit_ns(ns);
    shm_exit_ns(ns);
    kfree(ns);
    + atomic_dec(&nr_ipc_ns);
    }

    /**
    Index: linux-2.6.24/ipc/msg.c
    ===================================================================
    --- linux-2.6.24.orig/ipc/msg.c 2008-01-31 09:58:25.000000000 +0100
    +++ linux-2.6.24/ipc/msg.c 2008-01-31 10:08:49.000000000 +0100
    @@ -83,24 +83,28 @@ static int sysvipc_msg_proc_show(struct
    /*
    * Scale msgmni with the available lowmem size: the memory dedicated to msg
    * queues should occupy at most 1/MSG_MEM_SCALE of lowmem.
    - * This should be done staying within the (MSGMNI , IPCMNI) range.
    + * Also take into account the number of nsproxies created so far.
    + * This should be done staying within the (MSGMNI , IPCMNI/nr_ipc_ns) range.
    */
    static void recompute_msgmni(struct ipc_namespace *ns)
    {
    struct sysinfo i;
    unsigned long allowed;
    + int nb_ns;

    si_meminfo(&i);
    allowed = (((i.totalram - i.totalhigh) / MSG_MEM_SCALE) * i.mem_unit)
    / MSGMNB;
    + nb_ns = atomic_read(&nr_ipc_ns);
    + allowed /= nb_ns;

    if (allowed < MSGMNI) {
    ns->msg_ctlmni = MSGMNI;
    goto out_callback;
    }

    - if (allowed > IPCMNI) {
    - ns->msg_ctlmni = IPCMNI;
    + if (allowed > IPCMNI / nb_ns) {
    + ns->msg_ctlmni = IPCMNI / nb_ns;
    goto out_callback;
    }

    --


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