[Devel] [RFC][PATCH 07/16] Move alloc_pid call to copy_process

[Pavel Emelianov]

> Index: lx26-21-mm2/kernel/pid.c
> ===================================================================
> --- lx26-21-mm2.orig/kernel/pid.c	2007-05-22 16:59:46.000000000 -0700
> +++ lx26-21-mm2/kernel/pid.c	2007-05-22 17:06:48.000000000 -0700
> @@ -216,6 +216,10 @@ fastcall void free_pid(struct pid *pid)
>  	/* We can be called with write_lock_irq(&tasklist_lock) held */
>  	unsigned long flags;
>  
> +	/* check this here to keep copy_process() cleaner */
> +	if (unlikely(pid == &init_struct_pid))
> +		return;
> +

This looks ugly to me.
That's the same as if we put 
   if (ns == &init_pid_ns)
        return;
in put_pid_ns() call.

Such small struts of their own do not introduce any noticeable
effect, but when we have them in many places (and on fast patsh
like alloc_pid()) the performance hurts...


>  	spin_lock_irqsave(&pidmap_lock, flags);
>  	hlist_del_rcu(&pid->pid_chain);
>  	spin_unlock_irqrestore(&pidmap_lock, flags);
> @@ -224,12 +228,16 @@ fastcall void free_pid(struct pid *pid)
>  	call_rcu(&pid->rcu, delayed_put_pid);
>  }
>  
> -struct pid *alloc_pid(void)
> +struct pid *alloc_pid(enum copy_process_type copy_src)
>  {
>  	struct pid *pid;
>  	enum pid_type type;
>  	int nr = -1;
>  
> +	/* check this here to keep copy_process() cleaner */
> +	if (unlikely(copy_src == COPY_IDLE_PROCESS))
> +		return &init_struct_pid;
> +
>  	pid = kmem_cache_alloc(pid_cachep, GFP_KERNEL);
>  	if (!pid)
>  		goto out;
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