linux-kernel - Re: [PATCH v3 07/13] mm: Allocate kernel pages to the right memcg

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Date:	Fri, 28 Sep 2012 14:28:39 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Glauber Costa <glommer@...allels.com>
Cc:	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	kamezawa.hiroyu@...fujitsu.com, devel@...nvz.org,
	Tejun Heo <tj@...nel.org>, linux-mm@...ck.org,
	Suleiman Souhlal <suleiman@...gle.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	David Rientjes <rientjes@...gle.com>,
	Christoph Lameter <cl@...ux.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	Michal Hocko <mhocko@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v3 07/13] mm: Allocate kernel pages to the right memcg

On Fri, Sep 28, 2012 at 01:43:47PM +0400, Glauber Costa wrote:
> On 09/27/2012 05:50 PM, Mel Gorman wrote:
> >> +void __free_accounted_pages(struct page *page, unsigned int order)
> >> > +{
> >> > +	memcg_kmem_uncharge_page(page, order);
> >> > +	__free_pages(page, order);
> >> > +}
> >> > +
> >> > +void free_accounted_pages(unsigned long addr, unsigned int order)
> >> > +{
> >> > +	if (addr != 0) {
> >> > +		VM_BUG_ON(!virt_addr_valid((void *)addr));
> > This is probably overkill. If it's invalid, the next line is likely to
> > blow up anyway. It's no biggie.
> > 
> 
> So this is here because it is in free_pages() as well. If it blows, at
> least we know precisely why (if debugging), and VM_BUG_ON() is only
> compiled in when CONFIG_DEBUG_VM.
> 

Ah, I see.

> But I'm fine with either.
> Should it stay or should it go ?
> 

It can stay. It makes sense that it look similar to free_pages() and as
you say, it makes debugging marginally easier.


-- 
Mel Gorman
SUSE Labs
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