Re: [PATCH 1/2] memcg: dirty pages accounting and limiting infrastructure

[Andrea Righi <arighi@develer.com>]

On Mon, Feb 22, 2010 at 09:22:42AM +0900, KAMEZAWA Hiroyuki wrote:

[snip]

> > +static unsigned long get_dirty_bytes(struct mem_cgroup *memcg)
> > +{
> > +	struct cgroup *cgrp = memcg->css.cgroup;
> > +	unsigned long dirty_bytes;
> > +
> > +	/* root ? */
> > +	if (cgrp->parent == NULL)
> > +		return vm_dirty_bytes;
> 
> We have mem_cgroup_is_root() macro.
> 
> > +
> > +	spin_lock(&memcg->reclaim_param_lock);
> > +	dirty_bytes = memcg->dirty_bytes;
> > +	spin_unlock(&memcg->reclaim_param_lock);
> > +
> > +	return dirty_bytes;
> > +}
> Hmm...do we need spinlock ? You use "unsigned long", then, read-write
> is always atomic if not read-modify-write.

I think I simply copy&paste the memcg->swappiness case. But I agree,
read-write should be atomic.

-Andrea