linux-kernel - Re: [PATCH v2 1/3] mm: rework memcg kernel stack accounting

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Message-ID: <20180824075201.GZ29735@dhcp22.suse.cz>
Date:   Fri, 24 Aug 2018 09:52:01 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Roman Gushchin <guro@...com>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, Johannes Weiner <hannes@...xchg.org>,
        Andy Lutomirski <luto@...nel.org>,
        Konstantin Khlebnikov <koct9i@...il.com>,
        Tejun Heo <tj@...nel.org>, Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [PATCH v2 1/3] mm: rework memcg kernel stack accounting

On Thu 23-08-18 09:23:50, Roman Gushchin wrote:
> On Wed, Aug 22, 2018 at 04:12:13PM +0200, Michal Hocko wrote:
[...]
> > > @@ -248,9 +253,20 @@ static unsigned long *alloc_thread_stack_node(struct task_struct *tsk, int node)
> > >  static inline void free_thread_stack(struct task_struct *tsk)
> > >  {
> > >  #ifdef CONFIG_VMAP_STACK
> > > -	if (task_stack_vm_area(tsk)) {
> > > +	struct vm_struct *vm = task_stack_vm_area(tsk);
> > > +
> > > +	if (vm) {
> > >  		int i;
> > >  
> > > +		for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
> > > +			mod_memcg_page_state(vm->pages[i],
> > > +					     MEMCG_KERNEL_STACK_KB,
> > > +					     -(int)(PAGE_SIZE / 1024));
> > > +
> > > +			memcg_kmem_uncharge(vm->pages[i],
> > > +					    compound_order(vm->pages[i]));
> > 
> > when do we have order > 0 here?
> 
> I guess, it's not possible, but hard-coded 1 looked a bit crappy.
> Do you think it's better?

I guess you meant 0 here. Well, I do not mind, I was just wondering
whether I am missing something.
-- 
Michal Hocko
SUSE Labs